Re: [M100] REXCPM for Model 200?

[Stephen Adolph]

Soldered.  Would be nice to make that easier.

On Saturday, September 3, 2022, B 9  wrote:

> I agree with Birt, those micrograbbers are finicky. How does the wire for
> RexCPM connect securely in the T102?
>
> —b9
>
> On Mon, Aug 29, 2022 at 5:25 PM Stephen Adolph 
> wrote:
>
>> Bit of a step forward in terms of REXCPM for T200.
>>
>> In experiments on a real T200 (not virtualT), I get the following nice
>> result.
>>
>> Question:  What memory is accessed in the "address hole" from 8000-9FFF"
>> when Option ROM is selected (BANK3)?
>> - ideally CP/M needs a full 64k
>> - we have ram from A000-
>> - we have "REXCPM RAM" from -7FFF (when BANK3 is active)
>> - ... and,  we know that the 2nd 8K MAIN ROM is accessed from 8000-9FFF
>> when BANK1 is active.
>>
>> Turns out that the Option ROM is actually chip selected for the entire
>> address range from -7FFF AND 8000-9FFF!
>> --> when I run a "peeker" program that switches the option ROM on, and
>> then reads back the memory value from an address, the laptop responds with
>> the SAME value from -1FFF and 8000-9FFF.
>>
>> --> if the option ROM socket had the A15 signal, then it could
>> distinguish between the addresses.
>>
>> Said another way,
>> If the Option ROM socket had a 33rd signal, A15, it could support 40KB
>> worth of ROM memory.
>>
>> Maybe we can use something like this as an easy way to grab A15 from an
>> internal location?
>>
>> https://www.ebay.ca/itm/253076010211?hash=item3aec8174e3:g:
>> U6cAAOSwbmdZgrNP=enc%3AAQAH8O%2BKwe9wfSB0ZCf9NL04BWAEWnVZHPJ
>> %2BT%2BHLBzEY1gVeSf7OTaXsaxnr6JwWChHUHT7prORrrMSMiHFq%2F1%
>> 2Bjtp6bDA8e9kV2jiEeIOs3%2BGUpm7kzMlXvBrqcxGnckEHOk6dda
>> qGdNkxwD%2BXT3mw6PRS4fvgyEb6F%2B%2B6n1HNINZA87pEbiSn7B6AZkEVbVi
>> f2zL7S0cJbabZHXoFcWtu0WhUYfu56fE4OdjuyRx%2BafocbP2PnQ%2Fn%
>> 2Fu9tCqD9TYlXbA7n%2F75Ph6UZCTUtcgh36XdeqMgK5xDfYo9C8GnRVZRhmXRc8TM82NB%
>> 2FmMpp7aSL4fA%3D%3D%7Ctkp%3ABk9SR5DLx7_dYA
>>
>>
>> Steve
>>
>> Therefore, the only "additional signal" needed, for REXCPM in T200, is to
>> bring A15 to the memory area.
>>
>>
>>

Re: [M100] REXCPM for Model 200?

[B 9]

I agree with Birt, those micrograbbers are finicky. How does the wire for
RexCPM connect securely in the T102?

—b9

On Mon, Aug 29, 2022 at 5:25 PM Stephen Adolph  wrote:

> Bit of a step forward in terms of REXCPM for T200.
>
> In experiments on a real T200 (not virtualT), I get the following nice
> result.
>
> Question:  What memory is accessed in the "address hole" from 8000-9FFF"
> when Option ROM is selected (BANK3)?
> - ideally CP/M needs a full 64k
> - we have ram from A000-
> - we have "REXCPM RAM" from -7FFF (when BANK3 is active)
> - ... and,  we know that the 2nd 8K MAIN ROM is accessed from 8000-9FFF
> when BANK1 is active.
>
> Turns out that the Option ROM is actually chip selected for the entire
> address range from -7FFF AND 8000-9FFF!
> --> when I run a "peeker" program that switches the option ROM on, and
> then reads back the memory value from an address, the laptop responds with
> the SAME value from -1FFF and 8000-9FFF.
>
> --> if the option ROM socket had the A15 signal, then it could distinguish
> between the addresses.
>
> Said another way,
> If the Option ROM socket had a 33rd signal, A15, it could support 40KB
> worth of ROM memory.
>
> Maybe we can use something like this as an easy way to grab A15 from an
> internal location?
>
>
> https://www.ebay.ca/itm/253076010211?hash=item3aec8174e3:g:U6cAAOSwbmdZgrNP=enc%3AAQAH8O%2BKwe9wfSB0ZCf9NL04BWAEWnVZHPJ%2BT%2BHLBzEY1gVeSf7OTaXsaxnr6JwWChHUHT7prORrrMSMiHFq%2F1%2Bjtp6bDA8e9kV2jiEeIOs3%2BGUpm7kzMlXvBrqcxGnckEHOk6ddaqGdNkxwD%2BXT3mw6PRS4fvgyEb6F%2B%2B6n1HNINZA87pEbiSn7B6AZkEVbVif2zL7S0cJbabZHXoFcWtu0WhUYfu56fE4OdjuyRx%2BafocbP2PnQ%2Fn%2Fu9tCqD9TYlXbA7n%2F75Ph6UZCTUtcgh36XdeqMgK5xDfYo9C8GnRVZRhmXRc8TM82NB%2FmMpp7aSL4fA%3D%3D%7Ctkp%3ABk9SR5DLx7_dYA
>
>
> Steve
>
> Therefore, the only "additional signal" needed, for REXCPM in T200, is to
> bring A15 to the memory area.
>
>
>

Re: [M100] REXCPM for Model 200?

[birt_j]

I find quality micrograbbers ‘OK’ for a test situation for a permanent 
connection, particularly on something portable I don’t think they are a good 
solution. Cheap micrograbbers fall off if you look at them cross eyed.

 

Jeff Birt

 

From: M100  On Behalf Of Stephen Adolph
Sent: Monday, August 29, 2022 7:24 PM
To: m...@bitchin100.com
Subject: Re: [M100] REXCPM for Model 200?

 

Bit of a step forward in terms of REXCPM for T200.

 

In experiments on a real T200 (not virtualT), I get the following nice result.

 

Question:  What memory is accessed in the "address hole" from 8000-9FFF" when 
Option ROM is selected (BANK3)?

- ideally CP/M needs a full 64k

- we have ram from A000-

- we have "REXCPM RAM" from -7FFF (when BANK3 is active)

- ... and,  we know that the 2nd 8K MAIN ROM is accessed from 8000-9FFF when 
BANK1 is active.

 

Turns out that the Option ROM is actually chip selected for the entire address 
range from -7FFF AND 8000-9FFF!

--> when I run a "peeker" program that switches the option ROM on, and then 
reads back the memory value from an address, the laptop responds with the SAME 
value from -1FFF and 8000-9FFF.

 

--> if the option ROM socket had the A15 signal, then it could distinguish 
between the addresses.

 

Said another way, 

If the Option ROM socket had a 33rd signal, A15, it could support 40KB worth of 
ROM memory.

 

Maybe we can use something like this as an easy way to grab A15 from an 
internal location?

 

https://www.ebay.ca/itm/253076010211?hash=item3aec8174e3:g:U6cAAOSwbmdZgrNP 
<https://www.ebay.ca/itm/253076010211?hash=item3aec8174e3:g:U6cAAOSwbmdZgrNP=enc%3AAQAH8O%2BKwe9wfSB0ZCf9NL04BWAEWnVZHPJ%2BT%2BHLBzEY1gVeSf7OTaXsaxnr6JwWChHUHT7prORrrMSMiHFq%2F1%2Bjtp6bDA8e9kV2jiEeIOs3%2BGUpm7kzMlXvBrqcxGnckEHOk6ddaqGdNkxwD%2BXT3mw6PRS4fvgyEb6F%2B%2B6n1HNINZA87pEbiSn7B6AZkEVbVif2zL7S0cJbabZHXoFcWtu0WhUYfu56fE4OdjuyRx%2BafocbP2PnQ%2Fn%2Fu9tCqD9TYlXbA7n%2F75Ph6UZCTUtcgh36XdeqMgK5xDfYo9C8GnRVZRhmXRc8TM82NB%2FmMpp7aSL4fA%3D%3D%7Ctkp%3ABk9SR5DLx7_dYA>
 
=enc%3AAQAH8O%2BKwe9wfSB0ZCf9NL04BWAEWnVZHPJ%2BT%2BHLBzEY1gVeSf7OTaXsaxnr6JwWChHUHT7prORrrMSMiHFq%2F1%2Bjtp6bDA8e9kV2jiEeIOs3%2BGUpm7kzMlXvBrqcxGnckEHOk6ddaqGdNkxwD%2BXT3mw6PRS4fvgyEb6F%2B%2B6n1HNINZA87pEbiSn7B6AZkEVbVif2zL7S0cJbabZHXoFcWtu0WhUYfu56fE4OdjuyRx%2BafocbP2PnQ%2Fn%2Fu9tCqD9TYlXbA7n%2F75Ph6UZCTUtcgh36XdeqMgK5xDfYo9C8GnRVZRhmXRc8TM82NB%2FmMpp7aSL4fA%3D%3D%7Ctkp%3ABk9SR5DLx7_dYA

 

 

Steve

 

Therefore, the only "additional signal" needed, for REXCPM in T200, is to bring 
A15 to the memory area.

 

 

Re: [M100] REXCPM for Model 200?

[Stephen Adolph]

Bit of a step forward in terms of REXCPM for T200.

In experiments on a real T200 (not virtualT), I get the following nice
result.

Question:  What memory is accessed in the "address hole" from 8000-9FFF"
when Option ROM is selected (BANK3)?
- ideally CP/M needs a full 64k
- we have ram from A000-
- we have "REXCPM RAM" from -7FFF (when BANK3 is active)
- ... and,  we know that the 2nd 8K MAIN ROM is accessed from 8000-9FFF
when BANK1 is active.

Turns out that the Option ROM is actually chip selected for the entire
address range from -7FFF AND 8000-9FFF!
--> when I run a "peeker" program that switches the option ROM on, and then
reads back the memory value from an address, the laptop responds with the
SAME value from -1FFF and 8000-9FFF.

--> if the option ROM socket had the A15 signal, then it could distinguish
between the addresses.

Said another way,
If the Option ROM socket had a 33rd signal, A15, it could support 40KB
worth of ROM memory.

Maybe we can use something like this as an easy way to grab A15 from an
internal location?

https://www.ebay.ca/itm/253076010211?hash=item3aec8174e3:g:U6cAAOSwbmdZgrNP=enc%3AAQAH8O%2BKwe9wfSB0ZCf9NL04BWAEWnVZHPJ%2BT%2BHLBzEY1gVeSf7OTaXsaxnr6JwWChHUHT7prORrrMSMiHFq%2F1%2Bjtp6bDA8e9kV2jiEeIOs3%2BGUpm7kzMlXvBrqcxGnckEHOk6ddaqGdNkxwD%2BXT3mw6PRS4fvgyEb6F%2B%2B6n1HNINZA87pEbiSn7B6AZkEVbVif2zL7S0cJbabZHXoFcWtu0WhUYfu56fE4OdjuyRx%2BafocbP2PnQ%2Fn%2Fu9tCqD9TYlXbA7n%2F75Ph6UZCTUtcgh36XdeqMgK5xDfYo9C8GnRVZRhmXRc8TM82NB%2FmMpp7aSL4fA%3D%3D%7Ctkp%3ABk9SR5DLx7_dYA


Steve

Therefore, the only "additional signal" needed, for REXCPM in T200, is to
bring A15 to the memory area.

Re: [M100] REXCPM for Model 200?

[B 9]

A wire sounds good enough for me. I tried to trace the PCB to figure out
where A15 could most easily be tapped, but the resolution of the PCB scan
from the Tandy 200 Service Manual is too low.

—b9


On Wed, May 25, 2022 at 7:34 PM Stephen Adolph  wrote:

> Well,
> Looking at the REXCPM board, it is possible to go from 3 signals on the
> jumper to 4.
> This would allow for A15 to be brought in, and to identify the special
> case where /BANK3 is zero but the address bus is 8000-9FFF.
> At first blush I can't think of a good way to solve this other than by
> adding a wire.
>
> Which puts the T200 install on the same page as T102, with a single wire
> required.
>
>
> On Wed, May 25, 2022 at 10:16 PM Stephen Adolph 
> wrote:
>
>> AH, I see your point.
>> I stand corrected, A15 is not on the socket.
>> [image: image.png]
>>
>> So, maybe your suggestion works; is A15 needed at all?
>>
>> Yes, I think it is needed.
>>
>> How would you tell the difference between these two addresses, from the
>> perspective of REXCPM?
>>
>>   vs 8000.
>> Both have /BANK3 = 0, and /BANK6=1.  And A14 to A0 = 000.
>>
>>
>> Seems like you gotta have an additional signal, A15.  And A15 is NOT on
>> the memory card.  That means you would need to jumper in from inside the
>> case.
>>
>>
>> Thanks, good discussion. I think I got all excited but I forgot which
>> part of the address was multiplexed!!
>>
>>
>>
>> On Wed, May 25, 2022 at 10:08 PM Stephen Adolph 
>> wrote:
>>
>>> Couple of comments.
>>>
>>> Agree with your rule, but REXCPM is even more fancy.
>>>
>>> It supports 32k bank switching in  to 7FFF and 2 banks of 16k
>>> switched at 8000 to BFFF and C000 to .  So REXCPM has to differentiate
>>> a bit based on which bank is indicated.
>>>
>>> All this bank switching to support RAM disk as well as general option
>>> rom switching, plus general ram banking.
>>>
>>> I agree the service manual isnt clear.  But I know from experience that
>>> ALE can latch A8 to A15 in T200 and M100 option rom socket.
>>>
>>> One diagram does make it clear though.  I'll snip and send separately.
>>>
>>> 8085 in general has a multiplexed address bus.
>>>
>>>
>>>
>>> On Wednesday, May 25, 2022, B 9  wrote:
>>>
 Yes, that helps quite a bit. Thank you.

 One more question: If you are already handling situations 1 & 3 — bank3
 is low and bank 6 is high for both, so A15 must be checked — why not reduce
 the scenarios to a single rule:

- If either bank3 or bank6 is low, address is 0 to , rexcpm
responds.

 —b9

 P.S. Where can I read more about the data latched in by ALE? The Tandy
 200 service manual and technical reference make it look like the AD bus is
 holding only the lowest 8 bits of the memory address, A7 to A0, so I do not
 yet understand how it contains A15.


 On Wed, May 25, 2022 at 6:10 PM Stephen Adolph 
 wrote:

> when bank3 is low, address  to 7fff, bank6 is high, rexcpm
> responds.
>
> When bank6 is low, address a000 to , bank3 is high, rexcpm responds
>
> When bank3 is low, address 8000 to 9fff, bank6 is high, rexcpm
> responds.
>
> All of these scenarios are unique.  Cpm gets 64k when option rom and
> optikn ram 2 are engaged.
>
> Yah?  Hope that helps.
>
> Steve
>
>
>
>
> On Wednesday, May 25, 2022, B 9  wrote:
>
>> I'm a little confused.
>>
>> It sounds like you're selecting on /BANK3 = 0 (option ROM selected)
>> AND  /BANK6 = 0 (expansion RAM selected). But, if I'm reading figure 4-6
>> from the service manual correctly, /BANK3=0 AND /BANK6=0 will always be
>> false because no two banks are ever selected at the same time. Decoders
>> AA0037 and AA0038 are mutually exclusive, governed by the same logic: NOT
>> (A15 AND (A14 OR A13)).
>>
>> That is, it appears that for addresses 8000 to 9FFF, bank 3 is
>> selected: /BANK3=0 and /BANK6=1.
>>
>> Or, am I missing something?
>>
>> —b9
>>
>> On Wed, May 25, 2022 at 5:41 PM Stephen Adolph 
>> wrote:
>>
>>> I've been thinking about it too.
>>>
>>> /BANK6 is perfect for selecting that ram bank for address A000 to
>>> .  No issue.
>>>
>>> I believe that  , when option rom is selected, it is actually
>>> selected for all addresses from  to 9FFF.
>>>
>>> Now about A15.  It is actually present in the socket because the AD
>>> bus is present and ALE is present.
>>>
>>> So all you need is a register to capture it. A15 is AD7 sampled by
>>> ALE.
>>>
>>> The T200 diagrams dont call the bus AD but it is.
>>>
>>> So, the T200 ram adapter needs to supply
>>> 1. Battery voltage
>>> 2. /WR
>>> 3. /BANK6  (and or BANK5)
>>>
>>> Three wires, the same as M100 REXCPM but with different logic
>>> implemented in the CPLD.
>>>
>>> For 

Re: [M100] REXCPM for Model 200?

[Stephen Adolph]

Well,
Looking at the REXCPM board, it is possible to go from 3 signals on the
jumper to 4.
This would allow for A15 to be brought in, and to identify the special case
where /BANK3 is zero but the address bus is 8000-9FFF.
At first blush I can't think of a good way to solve this other than by
adding a wire.

Which puts the T200 install on the same page as T102, with a single wire
required.


On Wed, May 25, 2022 at 10:16 PM Stephen Adolph 
wrote:

> AH, I see your point.
> I stand corrected, A15 is not on the socket.
> [image: image.png]
>
> So, maybe your suggestion works; is A15 needed at all?
>
> Yes, I think it is needed.
>
> How would you tell the difference between these two addresses, from the
> perspective of REXCPM?
>
>   vs 8000.
> Both have /BANK3 = 0, and /BANK6=1.  And A14 to A0 = 000.
>
>
> Seems like you gotta have an additional signal, A15.  And A15 is NOT on
> the memory card.  That means you would need to jumper in from inside the
> case.
>
>
> Thanks, good discussion. I think I got all excited but I forgot which part
> of the address was multiplexed!!
>
>
>
> On Wed, May 25, 2022 at 10:08 PM Stephen Adolph 
> wrote:
>
>> Couple of comments.
>>
>> Agree with your rule, but REXCPM is even more fancy.
>>
>> It supports 32k bank switching in  to 7FFF and 2 banks of 16k
>> switched at 8000 to BFFF and C000 to .  So REXCPM has to differentiate
>> a bit based on which bank is indicated.
>>
>> All this bank switching to support RAM disk as well as general option rom
>> switching, plus general ram banking.
>>
>> I agree the service manual isnt clear.  But I know from experience that
>> ALE can latch A8 to A15 in T200 and M100 option rom socket.
>>
>> One diagram does make it clear though.  I'll snip and send separately.
>>
>> 8085 in general has a multiplexed address bus.
>>
>>
>>
>> On Wednesday, May 25, 2022, B 9  wrote:
>>
>>> Yes, that helps quite a bit. Thank you.
>>>
>>> One more question: If you are already handling situations 1 & 3 — bank3
>>> is low and bank 6 is high for both, so A15 must be checked — why not reduce
>>> the scenarios to a single rule:
>>>
>>>- If either bank3 or bank6 is low, address is 0 to , rexcpm
>>>responds.
>>>
>>> —b9
>>>
>>> P.S. Where can I read more about the data latched in by ALE? The Tandy
>>> 200 service manual and technical reference make it look like the AD bus is
>>> holding only the lowest 8 bits of the memory address, A7 to A0, so I do not
>>> yet understand how it contains A15.
>>>
>>>
>>> On Wed, May 25, 2022 at 6:10 PM Stephen Adolph 
>>> wrote:
>>>
 when bank3 is low, address  to 7fff, bank6 is high, rexcpm responds.

 When bank6 is low, address a000 to , bank3 is high, rexcpm responds

 When bank3 is low, address 8000 to 9fff, bank6 is high, rexcpm responds.

 All of these scenarios are unique.  Cpm gets 64k when option rom and
 optikn ram 2 are engaged.

 Yah?  Hope that helps.

 Steve




 On Wednesday, May 25, 2022, B 9  wrote:

> I'm a little confused.
>
> It sounds like you're selecting on /BANK3 = 0 (option ROM selected)
> AND  /BANK6 = 0 (expansion RAM selected). But, if I'm reading figure 4-6
> from the service manual correctly, /BANK3=0 AND /BANK6=0 will always be
> false because no two banks are ever selected at the same time. Decoders
> AA0037 and AA0038 are mutually exclusive, governed by the same logic: NOT
> (A15 AND (A14 OR A13)).
>
> That is, it appears that for addresses 8000 to 9FFF, bank 3 is
> selected: /BANK3=0 and /BANK6=1.
>
> Or, am I missing something?
>
> —b9
>
> On Wed, May 25, 2022 at 5:41 PM Stephen Adolph 
> wrote:
>
>> I've been thinking about it too.
>>
>> /BANK6 is perfect for selecting that ram bank for address A000 to
>> .  No issue.
>>
>> I believe that  , when option rom is selected, it is actually
>> selected for all addresses from  to 9FFF.
>>
>> Now about A15.  It is actually present in the socket because the AD
>> bus is present and ALE is present.
>>
>> So all you need is a register to capture it. A15 is AD7 sampled by
>> ALE.
>>
>> The T200 diagrams dont call the bus AD but it is.
>>
>> So, the T200 ram adapter needs to supply
>> 1. Battery voltage
>> 2. /WR
>> 3. /BANK6  (and or BANK5)
>>
>> Three wires, the same as M100 REXCPM but with different logic
>> implemented in the CPLD.
>>
>> For the record, in M100 and T102 REXCPM disables the internal ram by
>> manipulating RAMRST.  This isn't necessary for T200.  The option rams can
>> be replaced by REXCPM.  Back driving RAMRST takes only a few mA.
>>
>> So yeah I think it works.  I am thinking about a few little
>> experiments to confirm my suspicions.
>>
>> Still a lot of firmware and software work to do.  I already laid out
>> 

Re: [M100] REXCPM for Model 200?

[Stephen Adolph]

 AH, I see your point.
I stand corrected, A15 is not on the socket.
[image: image.png]

So, maybe your suggestion works; is A15 needed at all?

Yes, I think it is needed.

How would you tell the difference between these two addresses, from the
perspective of REXCPM?

  vs 8000.
Both have /BANK3 = 0, and /BANK6=1.  And A14 to A0 = 000.


Seems like you gotta have an additional signal, A15.  And A15 is NOT on the
memory card.  That means you would need to jumper in from inside the case.


Thanks, good discussion. I think I got all excited but I forgot which part
of the address was multiplexed!!



On Wed, May 25, 2022 at 10:08 PM Stephen Adolph 
wrote:

> Couple of comments.
>
> Agree with your rule, but REXCPM is even more fancy.
>
> It supports 32k bank switching in  to 7FFF and 2 banks of 16k switched
> at 8000 to BFFF and C000 to .  So REXCPM has to differentiate a bit
> based on which bank is indicated.
>
> All this bank switching to support RAM disk as well as general option rom
> switching, plus general ram banking.
>
> I agree the service manual isnt clear.  But I know from experience that
> ALE can latch A8 to A15 in T200 and M100 option rom socket.
>
> One diagram does make it clear though.  I'll snip and send separately.
>
> 8085 in general has a multiplexed address bus.
>
>
>
> On Wednesday, May 25, 2022, B 9  wrote:
>
>> Yes, that helps quite a bit. Thank you.
>>
>> One more question: If you are already handling situations 1 & 3 — bank3
>> is low and bank 6 is high for both, so A15 must be checked — why not reduce
>> the scenarios to a single rule:
>>
>>- If either bank3 or bank6 is low, address is 0 to , rexcpm
>>responds.
>>
>> —b9
>>
>> P.S. Where can I read more about the data latched in by ALE? The Tandy
>> 200 service manual and technical reference make it look like the AD bus is
>> holding only the lowest 8 bits of the memory address, A7 to A0, so I do not
>> yet understand how it contains A15.
>>
>>
>> On Wed, May 25, 2022 at 6:10 PM Stephen Adolph 
>> wrote:
>>
>>> when bank3 is low, address  to 7fff, bank6 is high, rexcpm responds.
>>>
>>> When bank6 is low, address a000 to , bank3 is high, rexcpm responds
>>>
>>> When bank3 is low, address 8000 to 9fff, bank6 is high, rexcpm responds.
>>>
>>> All of these scenarios are unique.  Cpm gets 64k when option rom and
>>> optikn ram 2 are engaged.
>>>
>>> Yah?  Hope that helps.
>>>
>>> Steve
>>>
>>>
>>>
>>>
>>> On Wednesday, May 25, 2022, B 9  wrote:
>>>
 I'm a little confused.

 It sounds like you're selecting on /BANK3 = 0 (option ROM selected)
 AND  /BANK6 = 0 (expansion RAM selected). But, if I'm reading figure 4-6
 from the service manual correctly, /BANK3=0 AND /BANK6=0 will always be
 false because no two banks are ever selected at the same time. Decoders
 AA0037 and AA0038 are mutually exclusive, governed by the same logic: NOT
 (A15 AND (A14 OR A13)).

 That is, it appears that for addresses 8000 to 9FFF, bank 3 is
 selected: /BANK3=0 and /BANK6=1.

 Or, am I missing something?

 —b9

 On Wed, May 25, 2022 at 5:41 PM Stephen Adolph 
 wrote:

> I've been thinking about it too.
>
> /BANK6 is perfect for selecting that ram bank for address A000 to
> .  No issue.
>
> I believe that  , when option rom is selected, it is actually selected
> for all addresses from  to 9FFF.
>
> Now about A15.  It is actually present in the socket because the AD
> bus is present and ALE is present.
>
> So all you need is a register to capture it. A15 is AD7 sampled by ALE.
>
> The T200 diagrams dont call the bus AD but it is.
>
> So, the T200 ram adapter needs to supply
> 1. Battery voltage
> 2. /WR
> 3. /BANK6  (and or BANK5)
>
> Three wires, the same as M100 REXCPM but with different logic
> implemented in the CPLD.
>
> For the record, in M100 and T102 REXCPM disables the internal ram by
> manipulating RAMRST.  This isn't necessary for T200.  The option rams can
> be replaced by REXCPM.  Back driving RAMRST takes only a few mA.
>
> So yeah I think it works.  I am thinking about a few little
> experiments to confirm my suspicions.
>
> Still a lot of firmware and software work to do.  I already laid out
> the adapter. That's easy... ;)
>
>
>
>
>
>
> On Wednesday, May 25, 2022, B 9  wrote:
>
>> If you can get A15 without a blue wire, it does not seem that you
>> would need the new select signal based on /BANK6. Requests for 8000 to 
>> 9FFF
>> appear to already go to Bank 3, so you'd just need to detect addresses in
>> that range in the OPTION ROM. It looks like the service manual schematic
>> for bank select does that using NOT( A15 AND (A14 OR A13) ).
>>
>> —b9
>>
>>
>>
>>
>>
>> On Mon, May 16, 2022 at 3:57 PM Stephen 

Re: [M100] REXCPM for Model 200?

[Stephen Adolph]

Couple of comments.

Agree with your rule, but REXCPM is even more fancy.

It supports 32k bank switching in  to 7FFF and 2 banks of 16k switched
at 8000 to BFFF and C000 to .  So REXCPM has to differentiate a bit
based on which bank is indicated.

All this bank switching to support RAM disk as well as general option rom
switching, plus general ram banking.

I agree the service manual isnt clear.  But I know from experience that ALE
can latch A8 to A15 in T200 and M100 option rom socket.

One diagram does make it clear though.  I'll snip and send separately.

8085 in general has a multiplexed address bus.



On Wednesday, May 25, 2022, B 9  wrote:

> Yes, that helps quite a bit. Thank you.
>
> One more question: If you are already handling situations 1 & 3 — bank3 is
> low and bank 6 is high for both, so A15 must be checked — why not reduce
> the scenarios to a single rule:
>
>- If either bank3 or bank6 is low, address is 0 to , rexcpm
>responds.
>
> —b9
>
> P.S. Where can I read more about the data latched in by ALE? The Tandy 200
> service manual and technical reference make it look like the AD bus is
> holding only the lowest 8 bits of the memory address, A7 to A0, so I do not
> yet understand how it contains A15.
>
>
> On Wed, May 25, 2022 at 6:10 PM Stephen Adolph 
> wrote:
>
>> when bank3 is low, address  to 7fff, bank6 is high, rexcpm responds.
>>
>> When bank6 is low, address a000 to , bank3 is high, rexcpm responds
>>
>> When bank3 is low, address 8000 to 9fff, bank6 is high, rexcpm responds.
>>
>> All of these scenarios are unique.  Cpm gets 64k when option rom and
>> optikn ram 2 are engaged.
>>
>> Yah?  Hope that helps.
>>
>> Steve
>>
>>
>>
>>
>> On Wednesday, May 25, 2022, B 9  wrote:
>>
>>> I'm a little confused.
>>>
>>> It sounds like you're selecting on /BANK3 = 0 (option ROM selected) AND
>>> /BANK6 = 0 (expansion RAM selected). But, if I'm reading figure 4-6 from
>>> the service manual correctly, /BANK3=0 AND /BANK6=0 will always be false
>>> because no two banks are ever selected at the same time. Decoders AA0037
>>> and AA0038 are mutually exclusive, governed by the same logic: NOT (A15 AND
>>> (A14 OR A13)).
>>>
>>> That is, it appears that for addresses 8000 to 9FFF, bank 3 is selected:
>>> /BANK3=0 and /BANK6=1.
>>>
>>> Or, am I missing something?
>>>
>>> —b9
>>>
>>> On Wed, May 25, 2022 at 5:41 PM Stephen Adolph 
>>> wrote:
>>>
 I've been thinking about it too.

 /BANK6 is perfect for selecting that ram bank for address A000 to
 .  No issue.

 I believe that  , when option rom is selected, it is actually selected
 for all addresses from  to 9FFF.

 Now about A15.  It is actually present in the socket because the AD bus
 is present and ALE is present.

 So all you need is a register to capture it. A15 is AD7 sampled by ALE.

 The T200 diagrams dont call the bus AD but it is.

 So, the T200 ram adapter needs to supply
 1. Battery voltage
 2. /WR
 3. /BANK6  (and or BANK5)

 Three wires, the same as M100 REXCPM but with different logic
 implemented in the CPLD.

 For the record, in M100 and T102 REXCPM disables the internal ram by
 manipulating RAMRST.  This isn't necessary for T200.  The option rams can
 be replaced by REXCPM.  Back driving RAMRST takes only a few mA.

 So yeah I think it works.  I am thinking about a few little experiments
 to confirm my suspicions.

 Still a lot of firmware and software work to do.  I already laid out
 the adapter. That's easy... ;)






 On Wednesday, May 25, 2022, B 9  wrote:

> If you can get A15 without a blue wire, it does not seem that you
> would need the new select signal based on /BANK6. Requests for 8000 to 
> 9FFF
> appear to already go to Bank 3, so you'd just need to detect addresses in
> that range in the OPTION ROM. It looks like the service manual schematic
> for bank select does that using NOT( A15 AND (A14 OR A13) ).
>
> —b9
>
>
>
>
>
> On Mon, May 16, 2022 at 3:57 PM Stephen Adolph 
> wrote:
>
>> I took a fresh look at the T200 "all ram mode" which would be
>> needed for REXCPM to work (nicely).
>> Summary: it is actually feasible I believe to implement an all RAM
>> mode fairly easily, which would support CP/M nicely.
>>
>> *Issue 1.  The 8k ROM at 8000-9FFF*
>> * as shown on the schematic, the M15 ROM is only enabled when /BANK1
>> is low and A15 is high.
>>(also reference the 8k rom datasheet in the tech reference manual)
>> * also as shown on the schematic, the M13 32k ROM is only enabled
>> when /BANK1 is low and A15 is low.
>>
>> *SO - the 8k range is only active in /BANK1.*
>>
>> *Issue 2.  Creating an all RAM mode*
>> * /BANK3 enables the option ROM socket for -7FFF address range
>> * /BANK6 

Re: [M100] REXCPM for Model 200?

[B 9]

Yes, that helps quite a bit. Thank you.

One more question: If you are already handling situations 1 & 3 — bank3 is
low and bank 6 is high for both, so A15 must be checked — why not reduce
the scenarios to a single rule:

   - If either bank3 or bank6 is low, address is 0 to , rexcpm responds.

—b9

P.S. Where can I read more about the data latched in by ALE? The Tandy 200
service manual and technical reference make it look like the AD bus is
holding only the lowest 8 bits of the memory address, A7 to A0, so I do not
yet understand how it contains A15.


On Wed, May 25, 2022 at 6:10 PM Stephen Adolph  wrote:

> when bank3 is low, address  to 7fff, bank6 is high, rexcpm responds.
>
> When bank6 is low, address a000 to , bank3 is high, rexcpm responds
>
> When bank3 is low, address 8000 to 9fff, bank6 is high, rexcpm responds.
>
> All of these scenarios are unique.  Cpm gets 64k when option rom and
> optikn ram 2 are engaged.
>
> Yah?  Hope that helps.
>
> Steve
>
>
>
>
> On Wednesday, May 25, 2022, B 9  wrote:
>
>> I'm a little confused.
>>
>> It sounds like you're selecting on /BANK3 = 0 (option ROM selected) AND
>> /BANK6 = 0 (expansion RAM selected). But, if I'm reading figure 4-6 from
>> the service manual correctly, /BANK3=0 AND /BANK6=0 will always be false
>> because no two banks are ever selected at the same time. Decoders AA0037
>> and AA0038 are mutually exclusive, governed by the same logic: NOT (A15 AND
>> (A14 OR A13)).
>>
>> That is, it appears that for addresses 8000 to 9FFF, bank 3 is selected:
>> /BANK3=0 and /BANK6=1.
>>
>> Or, am I missing something?
>>
>> —b9
>>
>> On Wed, May 25, 2022 at 5:41 PM Stephen Adolph 
>> wrote:
>>
>>> I've been thinking about it too.
>>>
>>> /BANK6 is perfect for selecting that ram bank for address A000 to .
>>> No issue.
>>>
>>> I believe that  , when option rom is selected, it is actually selected
>>> for all addresses from  to 9FFF.
>>>
>>> Now about A15.  It is actually present in the socket because the AD bus
>>> is present and ALE is present.
>>>
>>> So all you need is a register to capture it. A15 is AD7 sampled by ALE.
>>>
>>> The T200 diagrams dont call the bus AD but it is.
>>>
>>> So, the T200 ram adapter needs to supply
>>> 1. Battery voltage
>>> 2. /WR
>>> 3. /BANK6  (and or BANK5)
>>>
>>> Three wires, the same as M100 REXCPM but with different logic
>>> implemented in the CPLD.
>>>
>>> For the record, in M100 and T102 REXCPM disables the internal ram by
>>> manipulating RAMRST.  This isn't necessary for T200.  The option rams can
>>> be replaced by REXCPM.  Back driving RAMRST takes only a few mA.
>>>
>>> So yeah I think it works.  I am thinking about a few little experiments
>>> to confirm my suspicions.
>>>
>>> Still a lot of firmware and software work to do.  I already laid out the
>>> adapter. That's easy... ;)
>>>
>>>
>>>
>>>
>>>
>>>
>>> On Wednesday, May 25, 2022, B 9  wrote:
>>>
 If you can get A15 without a blue wire, it does not seem that you would
 need the new select signal based on /BANK6. Requests for 8000 to 9FFF
 appear to already go to Bank 3, so you'd just need to detect addresses in
 that range in the OPTION ROM. It looks like the service manual schematic
 for bank select does that using NOT( A15 AND (A14 OR A13) ).

 —b9





 On Mon, May 16, 2022 at 3:57 PM Stephen Adolph 
 wrote:

> I took a fresh look at the T200 "all ram mode" which would be
> needed for REXCPM to work (nicely).
> Summary: it is actually feasible I believe to implement an all RAM
> mode fairly easily, which would support CP/M nicely.
>
> *Issue 1.  The 8k ROM at 8000-9FFF*
> * as shown on the schematic, the M15 ROM is only enabled when /BANK1
> is low and A15 is high.
>(also reference the 8k rom datasheet in the tech reference manual)
> * also as shown on the schematic, the M13 32k ROM is only enabled when
> /BANK1 is low and A15 is low.
>
> *SO - the 8k range is only active in /BANK1.*
>
> *Issue 2.  Creating an all RAM mode*
> * /BANK3 enables the option ROM socket for -7FFF address range
> * /BANK6 enables the 2nd option RAM socket for A000- address range.
> * a new select signal is needed for when /BANK3 = 0 (option rom
> selected) AND A15=1 (upper addresses) AND  /BANK6=0
> (so when we are using the option ROM, and address is in range
> 8000-9FFF)
>
> * A15 is available in the OPTION ROM socket indirectly; as shown in
> the service manual in Figure 4-3, the AD bus is provided to the option ROM
> socket, as is ALE.  This means that A15 is present on AD7 (D7) on the
> falling edge of ALE.
>
> *SO - by stealing /BANK6 from the 2nd Option RAM socket, REXCPM could
> be programmed to provide an all RAM mode.*
>
> *What's needed to make REXCPM support T200*
>
>1. A modified REXCPM that is able to deduce when to enable RAM in
> 

Re: [M100] REXCPM for Model 200?

[Stephen Adolph]

when bank3 is low, address  to 7fff, bank6 is high, rexcpm responds.

When bank6 is low, address a000 to , bank3 is high, rexcpm responds

When bank3 is low, address 8000 to 9fff, bank6 is high, rexcpm responds.

All of these scenarios are unique.  Cpm gets 64k when option rom and optikn
ram 2 are engaged.

Yah?  Hope that helps.

Steve




On Wednesday, May 25, 2022, B 9  wrote:

> I'm a little confused.
>
> It sounds like you're selecting on /BANK3 = 0 (option ROM selected) AND
> /BANK6 = 0 (expansion RAM selected). But, if I'm reading figure 4-6 from
> the service manual correctly, /BANK3=0 AND /BANK6=0 will always be false
> because no two banks are ever selected at the same time. Decoders AA0037
> and AA0038 are mutually exclusive, governed by the same logic: NOT (A15 AND
> (A14 OR A13)).
>
> That is, it appears that for addresses 8000 to 9FFF, bank 3 is selected:
> /BANK3=0 and /BANK6=1.
>
> Or, am I missing something?
>
> —b9
>
> On Wed, May 25, 2022 at 5:41 PM Stephen Adolph 
> wrote:
>
>> I've been thinking about it too.
>>
>> /BANK6 is perfect for selecting that ram bank for address A000 to .
>> No issue.
>>
>> I believe that  , when option rom is selected, it is actually selected
>> for all addresses from  to 9FFF.
>>
>> Now about A15.  It is actually present in the socket because the AD bus
>> is present and ALE is present.
>>
>> So all you need is a register to capture it. A15 is AD7 sampled by ALE.
>>
>> The T200 diagrams dont call the bus AD but it is.
>>
>> So, the T200 ram adapter needs to supply
>> 1. Battery voltage
>> 2. /WR
>> 3. /BANK6  (and or BANK5)
>>
>> Three wires, the same as M100 REXCPM but with different logic implemented
>> in the CPLD.
>>
>> For the record, in M100 and T102 REXCPM disables the internal ram by
>> manipulating RAMRST.  This isn't necessary for T200.  The option rams can
>> be replaced by REXCPM.  Back driving RAMRST takes only a few mA.
>>
>> So yeah I think it works.  I am thinking about a few little experiments
>> to confirm my suspicions.
>>
>> Still a lot of firmware and software work to do.  I already laid out the
>> adapter. That's easy... ;)
>>
>>
>>
>>
>>
>>
>> On Wednesday, May 25, 2022, B 9  wrote:
>>
>>> If you can get A15 without a blue wire, it does not seem that you would
>>> need the new select signal based on /BANK6. Requests for 8000 to 9FFF
>>> appear to already go to Bank 3, so you'd just need to detect addresses in
>>> that range in the OPTION ROM. It looks like the service manual schematic
>>> for bank select does that using NOT( A15 AND (A14 OR A13) ).
>>>
>>> —b9
>>>
>>>
>>>
>>>
>>>
>>> On Mon, May 16, 2022 at 3:57 PM Stephen Adolph 
>>> wrote:
>>>
 I took a fresh look at the T200 "all ram mode" which would be
 needed for REXCPM to work (nicely).
 Summary: it is actually feasible I believe to implement an all RAM mode
 fairly easily, which would support CP/M nicely.

 *Issue 1.  The 8k ROM at 8000-9FFF*
 * as shown on the schematic, the M15 ROM is only enabled when /BANK1 is
 low and A15 is high.
(also reference the 8k rom datasheet in the tech reference manual)
 * also as shown on the schematic, the M13 32k ROM is only enabled when
 /BANK1 is low and A15 is low.

 *SO - the 8k range is only active in /BANK1.*

 *Issue 2.  Creating an all RAM mode*
 * /BANK3 enables the option ROM socket for -7FFF address range
 * /BANK6 enables the 2nd option RAM socket for A000- address range.
 * a new select signal is needed for when /BANK3 = 0 (option rom
 selected) AND A15=1 (upper addresses) AND  /BANK6=0
 (so when we are using the option ROM, and address is in range
 8000-9FFF)

 * A15 is available in the OPTION ROM socket indirectly; as shown in the
 service manual in Figure 4-3, the AD bus is provided to the option ROM
 socket, as is ALE.  This means that A15 is present on AD7 (D7) on the
 falling edge of ALE.

 *SO - by stealing /BANK6 from the 2nd Option RAM socket, REXCPM could
 be programmed to provide an all RAM mode.*

 *What's needed to make REXCPM support T200*

1. A modified REXCPM that is able to deduce when to enable RAM in
the 8000-9FFF range.
2. an Adapter Board sitting in Option RAM #2, which sends 3 signals
to REXCPM  (1)  Battery voltage  (2) /RD signal and (3) /BANK6 signal.
3. an updated RXCMGR application
4. an updated "T200 CP/M"  IE the M100 CP/M modified to use the
T200 environment.
5. updated CP/M uilities
6. (VirtualT updated to support REXCPM for T200...)






 On Sun, May 15, 2022 at 5:35 PM Stephen Adolph 
 wrote:

> There would have to be a convenient plug and play ideally way to
> decode that.
> From what is present in the ram module compartment, I dont see a good
> solution.
> I'll take another look.
>
> On Sunday, May 15, 

Re: [M100] REXCPM for Model 200?

[B 9]

I'm a little confused.

It sounds like you're selecting on /BANK3 = 0 (option ROM selected) AND
/BANK6 = 0 (expansion RAM selected). But, if I'm reading figure 4-6 from
the service manual correctly, /BANK3=0 AND /BANK6=0 will always be false
because no two banks are ever selected at the same time. Decoders AA0037
and AA0038 are mutually exclusive, governed by the same logic: NOT (A15 AND
(A14 OR A13)).

That is, it appears that for addresses 8000 to 9FFF, bank 3 is selected:
/BANK3=0 and /BANK6=1.

Or, am I missing something?

—b9

On Wed, May 25, 2022 at 5:41 PM Stephen Adolph  wrote:

> I've been thinking about it too.
>
> /BANK6 is perfect for selecting that ram bank for address A000 to .
> No issue.
>
> I believe that  , when option rom is selected, it is actually selected for
> all addresses from  to 9FFF.
>
> Now about A15.  It is actually present in the socket because the AD bus is
> present and ALE is present.
>
> So all you need is a register to capture it. A15 is AD7 sampled by ALE.
>
> The T200 diagrams dont call the bus AD but it is.
>
> So, the T200 ram adapter needs to supply
> 1. Battery voltage
> 2. /WR
> 3. /BANK6  (and or BANK5)
>
> Three wires, the same as M100 REXCPM but with different logic implemented
> in the CPLD.
>
> For the record, in M100 and T102 REXCPM disables the internal ram by
> manipulating RAMRST.  This isn't necessary for T200.  The option rams can
> be replaced by REXCPM.  Back driving RAMRST takes only a few mA.
>
> So yeah I think it works.  I am thinking about a few little experiments to
> confirm my suspicions.
>
> Still a lot of firmware and software work to do.  I already laid out the
> adapter. That's easy... ;)
>
>
>
>
>
>
> On Wednesday, May 25, 2022, B 9  wrote:
>
>> If you can get A15 without a blue wire, it does not seem that you would
>> need the new select signal based on /BANK6. Requests for 8000 to 9FFF
>> appear to already go to Bank 3, so you'd just need to detect addresses in
>> that range in the OPTION ROM. It looks like the service manual schematic
>> for bank select does that using NOT( A15 AND (A14 OR A13) ).
>>
>> —b9
>>
>>
>>
>>
>>
>> On Mon, May 16, 2022 at 3:57 PM Stephen Adolph 
>> wrote:
>>
>>> I took a fresh look at the T200 "all ram mode" which would be needed for
>>> REXCPM to work (nicely).
>>> Summary: it is actually feasible I believe to implement an all RAM mode
>>> fairly easily, which would support CP/M nicely.
>>>
>>> *Issue 1.  The 8k ROM at 8000-9FFF*
>>> * as shown on the schematic, the M15 ROM is only enabled when /BANK1 is
>>> low and A15 is high.
>>>(also reference the 8k rom datasheet in the tech reference manual)
>>> * also as shown on the schematic, the M13 32k ROM is only enabled when
>>> /BANK1 is low and A15 is low.
>>>
>>> *SO - the 8k range is only active in /BANK1.*
>>>
>>> *Issue 2.  Creating an all RAM mode*
>>> * /BANK3 enables the option ROM socket for -7FFF address range
>>> * /BANK6 enables the 2nd option RAM socket for A000- address range.
>>> * a new select signal is needed for when /BANK3 = 0 (option rom
>>> selected) AND A15=1 (upper addresses) AND  /BANK6=0
>>> (so when we are using the option ROM, and address is in range
>>> 8000-9FFF)
>>>
>>> * A15 is available in the OPTION ROM socket indirectly; as shown in the
>>> service manual in Figure 4-3, the AD bus is provided to the option ROM
>>> socket, as is ALE.  This means that A15 is present on AD7 (D7) on the
>>> falling edge of ALE.
>>>
>>> *SO - by stealing /BANK6 from the 2nd Option RAM socket, REXCPM could be
>>> programmed to provide an all RAM mode.*
>>>
>>> *What's needed to make REXCPM support T200*
>>>
>>>1. A modified REXCPM that is able to deduce when to enable RAM in
>>>the 8000-9FFF range.
>>>2. an Adapter Board sitting in Option RAM #2, which sends 3 signals
>>>to REXCPM  (1)  Battery voltage  (2) /RD signal and (3) /BANK6 signal.
>>>3. an updated RXCMGR application
>>>4. an updated "T200 CP/M"  IE the M100 CP/M modified to use the T200
>>>environment.
>>>5. updated CP/M uilities
>>>6. (VirtualT updated to support REXCPM for T200...)
>>>
>>>
>>>
>>>
>>>
>>>
>>> On Sun, May 15, 2022 at 5:35 PM Stephen Adolph 
>>> wrote:
>>>
 There would have to be a convenient plug and play ideally way to decode
 that.
 From what is present in the ram module compartment, I dont see a good
 solution.
 I'll take another look.

 On Sunday, May 15, 2022, B 9  wrote:

> I, too, would love to see RexCPM for the Tandy 200.
>
> I apologize for my ignorance, but why is there a hole? For ROM? Would
> it be possible to bank out 8000 to 9FFF and replace it with RAM when
> running CPM?
>
> —B9
>
>
> On Sun, May 15, 2022 at 9:44 AM Stephen Adolph 
> wrote:
>
>> Hi
>>
>> At this time, no.   It would require some changes due to the unique
>> memory map in the T200 relative to the M100.
>>
>> I think the biggest 

Re: [M100] REXCPM for Model 200?

[Stephen Adolph]

I've been thinking about it too.

/BANK6 is perfect for selecting that ram bank for address A000 to .  No
issue.

I believe that  , when option rom is selected, it is actually selected for
all addresses from  to 9FFF.

Now about A15.  It is actually present in the socket because the AD bus is
present and ALE is present.

So all you need is a register to capture it. A15 is AD7 sampled by ALE.

The T200 diagrams dont call the bus AD but it is.

So, the T200 ram adapter needs to supply
1. Battery voltage
2. /WR
3. /BANK6  (and or BANK5)

Three wires, the same as M100 REXCPM but with different logic implemented
in the CPLD.

For the record, in M100 and T102 REXCPM disables the internal ram by
manipulating RAMRST.  This isn't necessary for T200.  The option rams can
be replaced by REXCPM.  Back driving RAMRST takes only a few mA.

So yeah I think it works.  I am thinking about a few little experiments to
confirm my suspicions.

Still a lot of firmware and software work to do.  I already laid out the
adapter. That's easy... ;)






On Wednesday, May 25, 2022, B 9  wrote:

> If you can get A15 without a blue wire, it does not seem that you would
> need the new select signal based on /BANK6. Requests for 8000 to 9FFF
> appear to already go to Bank 3, so you'd just need to detect addresses in
> that range in the OPTION ROM. It looks like the service manual schematic
> for bank select does that using NOT( A15 AND (A14 OR A13) ).
>
> —b9
>
>
>
>
>
> On Mon, May 16, 2022 at 3:57 PM Stephen Adolph 
> wrote:
>
>> I took a fresh look at the T200 "all ram mode" which would be needed for
>> REXCPM to work (nicely).
>> Summary: it is actually feasible I believe to implement an all RAM mode
>> fairly easily, which would support CP/M nicely.
>>
>> *Issue 1.  The 8k ROM at 8000-9FFF*
>> * as shown on the schematic, the M15 ROM is only enabled when /BANK1 is
>> low and A15 is high.
>>(also reference the 8k rom datasheet in the tech reference manual)
>> * also as shown on the schematic, the M13 32k ROM is only enabled when
>> /BANK1 is low and A15 is low.
>>
>> *SO - the 8k range is only active in /BANK1.*
>>
>> *Issue 2.  Creating an all RAM mode*
>> * /BANK3 enables the option ROM socket for -7FFF address range
>> * /BANK6 enables the 2nd option RAM socket for A000- address range.
>> * a new select signal is needed for when /BANK3 = 0 (option rom selected)
>> AND A15=1 (upper addresses) AND  /BANK6=0
>> (so when we are using the option ROM, and address is in range
>> 8000-9FFF)
>>
>> * A15 is available in the OPTION ROM socket indirectly; as shown in the
>> service manual in Figure 4-3, the AD bus is provided to the option ROM
>> socket, as is ALE.  This means that A15 is present on AD7 (D7) on the
>> falling edge of ALE.
>>
>> *SO - by stealing /BANK6 from the 2nd Option RAM socket, REXCPM could be
>> programmed to provide an all RAM mode.*
>>
>> *What's needed to make REXCPM support T200*
>>
>>1. A modified REXCPM that is able to deduce when to enable RAM in the
>>8000-9FFF range.
>>2. an Adapter Board sitting in Option RAM #2, which sends 3 signals
>>to REXCPM  (1)  Battery voltage  (2) /RD signal and (3) /BANK6 signal.
>>3. an updated RXCMGR application
>>4. an updated "T200 CP/M"  IE the M100 CP/M modified to use the T200
>>environment.
>>5. updated CP/M uilities
>>6. (VirtualT updated to support REXCPM for T200...)
>>
>>
>>
>>
>>
>>
>> On Sun, May 15, 2022 at 5:35 PM Stephen Adolph 
>> wrote:
>>
>>> There would have to be a convenient plug and play ideally way to decode
>>> that.
>>> From what is present in the ram module compartment, I dont see a good
>>> solution.
>>> I'll take another look.
>>>
>>> On Sunday, May 15, 2022, B 9  wrote:
>>>
 I, too, would love to see RexCPM for the Tandy 200.

 I apologize for my ignorance, but why is there a hole? For ROM? Would
 it be possible to bank out 8000 to 9FFF and replace it with RAM when
 running CPM?

 —B9


 On Sun, May 15, 2022 at 9:44 AM Stephen Adolph 
 wrote:

> Hi
>
> At this time, no.   It would require some changes due to the unique
> memory map in the T200 relative to the M100.
>
> I think the biggest issue is that an all ram mode is not clearly
> possible.  There would be a hole fro. 8000 to 9FFF.   That's not great for
> CPM.
>
> Steve
>
> On Saturday, May 14, 2022, Hiraghm  wrote:
>
>> Is there an equivalent to the Model 100 REXCPM rom for the Model 200?
>>
>>
>>

Re: [M100] REXCPM for Model 200?

[B 9]

If you can get A15 without a blue wire, it does not seem that you would
need the new select signal based on /BANK6. Requests for 8000 to 9FFF
appear to already go to Bank 3, so you'd just need to detect addresses in
that range in the OPTION ROM. It looks like the service manual schematic
for bank select does that using NOT( A15 AND (A14 OR A13) ).

—b9





On Mon, May 16, 2022 at 3:57 PM Stephen Adolph  wrote:

> I took a fresh look at the T200 "all ram mode" which would be needed for
> REXCPM to work (nicely).
> Summary: it is actually feasible I believe to implement an all RAM mode
> fairly easily, which would support CP/M nicely.
>
> *Issue 1.  The 8k ROM at 8000-9FFF*
> * as shown on the schematic, the M15 ROM is only enabled when /BANK1 is
> low and A15 is high.
>(also reference the 8k rom datasheet in the tech reference manual)
> * also as shown on the schematic, the M13 32k ROM is only enabled when
> /BANK1 is low and A15 is low.
>
> *SO - the 8k range is only active in /BANK1.*
>
> *Issue 2.  Creating an all RAM mode*
> * /BANK3 enables the option ROM socket for -7FFF address range
> * /BANK6 enables the 2nd option RAM socket for A000- address range.
> * a new select signal is needed for when /BANK3 = 0 (option rom selected)
> AND A15=1 (upper addresses) AND  /BANK6=0
> (so when we are using the option ROM, and address is in range
> 8000-9FFF)
>
> * A15 is available in the OPTION ROM socket indirectly; as shown in the
> service manual in Figure 4-3, the AD bus is provided to the option ROM
> socket, as is ALE.  This means that A15 is present on AD7 (D7) on the
> falling edge of ALE.
>
> *SO - by stealing /BANK6 from the 2nd Option RAM socket, REXCPM could be
> programmed to provide an all RAM mode.*
>
> *What's needed to make REXCPM support T200*
>
>1. A modified REXCPM that is able to deduce when to enable RAM in the
>8000-9FFF range.
>2. an Adapter Board sitting in Option RAM #2, which sends 3 signals to
>REXCPM  (1)  Battery voltage  (2) /RD signal and (3) /BANK6 signal.
>3. an updated RXCMGR application
>4. an updated "T200 CP/M"  IE the M100 CP/M modified to use the T200
>environment.
>5. updated CP/M uilities
>6. (VirtualT updated to support REXCPM for T200...)
>
>
>
>
>
>
> On Sun, May 15, 2022 at 5:35 PM Stephen Adolph 
> wrote:
>
>> There would have to be a convenient plug and play ideally way to decode
>> that.
>> From what is present in the ram module compartment, I dont see a good
>> solution.
>> I'll take another look.
>>
>> On Sunday, May 15, 2022, B 9  wrote:
>>
>>> I, too, would love to see RexCPM for the Tandy 200.
>>>
>>> I apologize for my ignorance, but why is there a hole? For ROM? Would it
>>> be possible to bank out 8000 to 9FFF and replace it with RAM when running
>>> CPM?
>>>
>>> —B9
>>>
>>>
>>> On Sun, May 15, 2022 at 9:44 AM Stephen Adolph 
>>> wrote:
>>>
 Hi

 At this time, no.   It would require some changes due to the unique
 memory map in the T200 relative to the M100.

 I think the biggest issue is that an all ram mode is not clearly
 possible.  There would be a hole fro. 8000 to 9FFF.   That's not great for
 CPM.

 Steve

 On Saturday, May 14, 2022, Hiraghm  wrote:

> Is there an equivalent to the Model 100 REXCPM rom for the Model 200?
>
>
>

Re: [M100] REXCPM for Model 200?

[B 9]

(Sorry for the random seeming reply. I had thought I had sent that earlier.)

On Wed, May 25, 2022 at 4:49 PM B 9  wrote:

> Let me see if I understand correctly. The main problem is that CPM
> requires the entire 64K of address space to be RAM. For the Model 100,
> REXCPM somehow is able to replace both the builtin ROM (0-7FFF) and RAM
> (8000-) with its own System RAM. That method will not work for the
> Model 200 in which the ROM goes from 0 to 9FFF and the RAM is in three
> banks at A000-.
>
> I tried to look up how REXCPM is able to switch out the ROM and RAM to see
> if I could find an analogous solution for the Model 200, but unfortunately
> REXCPM's Technical Information simply says, "Work in progress!!!"
> .
> I'm guessing that REXCPM is able to replace the lower 32KB on a Model 100
> simply by virtue of being an "OPTION ROM". I have no idea how it replaces
> the RAM.
>
> Despite the Model 200 BASIC ROM now going to 40KB, the service manual
> states that OPTION ROMs are limited to 32KB. I see that only fifteen
> address lines (32KB) go to the socket. But is that insurmountable? The
> diagram for the Bank Selection Circuit (SLA5080F0U) appears to select the
> ROM for addresses up to 9FFF, regardless of whether the ROM is bank 1
> (BASIC) or bank 3 (OPTION ROM). So, any OPTION ROM would already be filling
> in that hole from 8000 to 9, but with the data from 0 to 1FFF since it
> is missing *A₁₅*, the high bit of the address. Right?
>
> Correct me if I'm wrong — and I probably am — but theoretically couldn't
> one create an option ROM chip that has an extra input pin for *A₁₅* and
> have it work  to replace all 40KB of ROM with RAM? I'm imagining a blue
> wire for *A₁₅* connecting to, perhaps, pin 27 on chip M13, the
> supplemental 8KB of BASIC ROM.
>
> —B9
>
> On Sun, May 15, 2022 at 2:35 PM Stephen Adolph 
> wrote:
>
>> There would have to be a convenient plug and play ideally way to decode
>> that.
>> From what is present in the ram module compartment, I dont see a good
>> solution.
>> I'll take another look.
>>
>> On Sunday, May 15, 2022, B 9  wrote:
>>
>>> I, too, would love to see RexCPM for the Tandy 200.
>>>
>>> I apologize for my ignorance, but why is there a hole? For ROM? Would it
>>> be possible to bank out 8000 to 9FFF and replace it with RAM when running
>>> CPM?
>>>
>>> —B9
>>>
>>>
>>> On Sun, May 15, 2022 at 9:44 AM Stephen Adolph 
>>> wrote:
>>>
 Hi

 At this time, no.   It would require some changes due to the unique
 memory map in the T200 relative to the M100.

 I think the biggest issue is that an all ram mode is not clearly
 possible.  There would be a hole fro. 8000 to 9FFF.   That's not great for
 CPM.

 Steve

 On Saturday, May 14, 2022, Hiraghm  wrote:

> Is there an equivalent to the Model 100 REXCPM rom for the Model 200?
>
>
>

Re: [M100] REXCPM for Model 200?

[B 9]

Let me see if I understand correctly. The main problem is that CPM requires
the entire 64K of address space to be RAM. For the Model 100, REXCPM
somehow is able to replace both the builtin ROM (0-7FFF) and RAM
(8000-) with its own System RAM. That method will not work for the
Model 200 in which the ROM goes from 0 to 9FFF and the RAM is in three
banks at A000-.

I tried to look up how REXCPM is able to switch out the ROM and RAM to see
if I could find an analogous solution for the Model 200, but unfortunately
REXCPM's Technical Information simply says, "Work in progress!!!"
.
I'm guessing that REXCPM is able to replace the lower 32KB on a Model 100
simply by virtue of being an "OPTION ROM". I have no idea how it replaces
the RAM.

Despite the Model 200 BASIC ROM now going to 40KB, the service manual
states that OPTION ROMs are limited to 32KB. I see that only fifteen
address lines (32KB) go to the socket. But is that insurmountable? The
diagram for the Bank Selection Circuit (SLA5080F0U) appears to select the
ROM for addresses up to 9FFF, regardless of whether the ROM is bank 1
(BASIC) or bank 3 (OPTION ROM). So, any OPTION ROM would already be filling
in that hole from 8000 to 9, but with the data from 0 to 1FFF since it
is missing *A₁₅*, the high bit of the address. Right?

Correct me if I'm wrong — and I probably am — but theoretically couldn't
one create an option ROM chip that has an extra input pin for *A₁₅* and
have it work  to replace all 40KB of ROM with RAM? I'm imagining a blue
wire for *A₁₅* connecting to, perhaps, pin 27 on chip M13, the supplemental
8KB of BASIC ROM.

—B9

On Sun, May 15, 2022 at 2:35 PM Stephen Adolph  wrote:

> There would have to be a convenient plug and play ideally way to decode
> that.
> From what is present in the ram module compartment, I dont see a good
> solution.
> I'll take another look.
>
> On Sunday, May 15, 2022, B 9  wrote:
>
>> I, too, would love to see RexCPM for the Tandy 200.
>>
>> I apologize for my ignorance, but why is there a hole? For ROM? Would it
>> be possible to bank out 8000 to 9FFF and replace it with RAM when running
>> CPM?
>>
>> —B9
>>
>>
>> On Sun, May 15, 2022 at 9:44 AM Stephen Adolph 
>> wrote:
>>
>>> Hi
>>>
>>> At this time, no.   It would require some changes due to the unique
>>> memory map in the T200 relative to the M100.
>>>
>>> I think the biggest issue is that an all ram mode is not clearly
>>> possible.  There would be a hole fro. 8000 to 9FFF.   That's not great for
>>> CPM.
>>>
>>> Steve
>>>
>>> On Saturday, May 14, 2022, Hiraghm  wrote:
>>>
 Is there an equivalent to the Model 100 REXCPM rom for the Model 200?

Re: [M100] REXCPM for Model 200?

[Ken Pettit]

Hey Steve,

This makes sense!  Let me know if you plan to proceed and need help with 
number 6 below.  :)


Ken

On 5/16/22 3:57 PM, Stephen Adolph wrote:
I took a fresh look at the T200 "all ram mode" which would be 
needed for REXCPM to work (nicely).
Summary: it is actually feasible I believe to implement an all RAM 
mode fairly easily, which would support CP/M nicely.


*Issue 1.  The 8k ROM at 8000-9FFF*
* as shown on the schematic, the M15 ROM is only enabled when /BANK1 
is low and A15 is high.

   (also reference the 8k rom datasheet in the tech reference manual)
* also as shown on the schematic, the M13 32k ROM is only enabled when 
/BANK1 is low and A15 is low.


*SO - the 8k range is only active in /BANK1.*

*Issue 2.  Creating an all RAM mode*
* /BANK3 enables the option ROM socket for -7FFF address range
* /BANK6 enables the 2nd option RAM socket for A000- address range.
* a new select signal is needed for when /BANK3 = 0 (option rom 
selected) AND A15=1 (upper addresses) AND /BANK6=0
(so when we are using the option ROM, and address is in range 
8000-9FFF)


* A15 is available in the OPTION ROM socket indirectly; as shown in 
the service manual in Figure 4-3, the AD bus is provided to the option 
ROM socket, as is ALE.  This means that A15 is present on AD7 (D7) on 
the falling edge of ALE.


*SO - by stealing /BANK6 from the 2nd Option RAM socket, REXCPM could 
be programmed to provide an all RAM mode.*

*
*
*What's needed to make REXCPM support T200*

 1. A modified REXCPM that is able to deduce when to enable RAM in the
8000-9FFF range.
 2. an Adapter Board sitting in Option RAM #2, which sends 3 signals
to REXCPM  (1)  Battery voltage  (2) /RD signal and (3) /BANK6 signal.
 3. an updated RXCMGR application
 4. an updated "T200 CP/M"  IE the M100 CP/M modified to use the T200
environment.
 5. updated CP/M uilities
 6. (VirtualT updated to support REXCPM for T200...)




*
*

On Sun, May 15, 2022 at 5:35 PM Stephen Adolph > wrote:


There would have to be a convenient plug and play ideally way to
decode that.
From what is present in the ram module compartment, I dont see a
good solution.
I'll take another look.

On Sunday, May 15, 2022, B 9 mailto:hacke...@gmail.com>> wrote:

I, too, would love to see RexCPM for the Tandy 200.

I apologize for my ignorance, but why is there a hole? For
ROM? Would it be possible to bank out 8000 to 9FFF and replace
it with RAM when running CPM?

—B9


On Sun, May 15, 2022 at 9:44 AM Stephen Adolph
mailto:twospru...@gmail.com>> wrote:

Hi

At this time, no.   It would require some changes due to
the unique memory map in the T200 relative to the M100.

I think the biggest issue is that an all ram mode is not
clearly possible.  There would be a hole fro. 8000 to
9FFF.   That's not great for CPM.

Steve

On Saturday, May 14, 2022, Hiraghm mailto:hira...@hotmail.com>> wrote:

Is there an equivalent to the Model 100 REXCPM rom for
the Model 200?

Re: [M100] REXCPM for Model 200?

[Stephen Adolph]

I took a fresh look at the T200 "all ram mode" which would be needed for
REXCPM to work (nicely).
Summary: it is actually feasible I believe to implement an all RAM mode
fairly easily, which would support CP/M nicely.

*Issue 1.  The 8k ROM at 8000-9FFF*
* as shown on the schematic, the M15 ROM is only enabled when /BANK1 is low
and A15 is high.
   (also reference the 8k rom datasheet in the tech reference manual)
* also as shown on the schematic, the M13 32k ROM is only enabled when
/BANK1 is low and A15 is low.

*SO - the 8k range is only active in /BANK1.*

*Issue 2.  Creating an all RAM mode*
* /BANK3 enables the option ROM socket for -7FFF address range
* /BANK6 enables the 2nd option RAM socket for A000- address range.
* a new select signal is needed for when /BANK3 = 0 (option rom selected)
AND A15=1 (upper addresses) AND  /BANK6=0
(so when we are using the option ROM, and address is in range 8000-9FFF)

* A15 is available in the OPTION ROM socket indirectly; as shown in the
service manual in Figure 4-3, the AD bus is provided to the option ROM
socket, as is ALE.  This means that A15 is present on AD7 (D7) on the
falling edge of ALE.

*SO - by stealing /BANK6 from the 2nd Option RAM socket, REXCPM could be
programmed to provide an all RAM mode.*

*What's needed to make REXCPM support T200*

   1. A modified REXCPM that is able to deduce when to enable RAM in the
   8000-9FFF range.
   2. an Adapter Board sitting in Option RAM #2, which sends 3 signals to
   REXCPM  (1)  Battery voltage  (2) /RD signal and (3) /BANK6 signal.
   3. an updated RXCMGR application
   4. an updated "T200 CP/M"  IE the M100 CP/M modified to use the T200
   environment.
   5. updated CP/M uilities
   6. (VirtualT updated to support REXCPM for T200...)






On Sun, May 15, 2022 at 5:35 PM Stephen Adolph  wrote:

> There would have to be a convenient plug and play ideally way to decode
> that.
> From what is present in the ram module compartment, I dont see a good
> solution.
> I'll take another look.
>
> On Sunday, May 15, 2022, B 9  wrote:
>
>> I, too, would love to see RexCPM for the Tandy 200.
>>
>> I apologize for my ignorance, but why is there a hole? For ROM? Would it
>> be possible to bank out 8000 to 9FFF and replace it with RAM when running
>> CPM?
>>
>> —B9
>>
>>
>> On Sun, May 15, 2022 at 9:44 AM Stephen Adolph 
>> wrote:
>>
>>> Hi
>>>
>>> At this time, no.   It would require some changes due to the unique
>>> memory map in the T200 relative to the M100.
>>>
>>> I think the biggest issue is that an all ram mode is not clearly
>>> possible.  There would be a hole fro. 8000 to 9FFF.   That's not great for
>>> CPM.
>>>
>>> Steve
>>>
>>> On Saturday, May 14, 2022, Hiraghm  wrote:
>>>
 Is there an equivalent to the Model 100 REXCPM rom for the Model 200?

[M100] REXCPM for Model 200?

[Stephen Adolph]

There would have to be a convenient plug and play ideally way to decode
that.
>From what is present in the ram module compartment, I dont see a good
solution.
I'll take another look.

On Sunday, May 15, 2022, B 9  wrote:

> I, too, would love to see RexCPM for the Tandy 200.
>
> I apologize for my ignorance, but why is there a hole? For ROM? Would it
> be possible to bank out 8000 to 9FFF and replace it with RAM when running
> CPM?
>
> —B9
>
>
> On Sun, May 15, 2022 at 9:44 AM Stephen Adolph 
> wrote:
>
>> Hi
>>
>> At this time, no.   It would require some changes due to the unique
>> memory map in the T200 relative to the M100.
>>
>> I think the biggest issue is that an all ram mode is not clearly
>> possible.  There would be a hole fro. 8000 to 9FFF.   That's not great for
>> CPM.
>>
>> Steve
>>
>> On Saturday, May 14, 2022, Hiraghm  wrote:
>>
>>> Is there an equivalent to the Model 100 REXCPM rom for the Model 200?
>>>
>>>
>>>

Re: [M100] REXCPM for Model 200?

[B 9]

I, too, would love to see RexCPM for the Tandy 200.

I apologize for my ignorance, but why is there a hole? For ROM? Would it be
possible to bank out 8000 to 9FFF and replace it with RAM when running CPM?

—B9


On Sun, May 15, 2022 at 9:44 AM Stephen Adolph  wrote:

> Hi
>
> At this time, no.   It would require some changes due to the unique memory
> map in the T200 relative to the M100.
>
> I think the biggest issue is that an all ram mode is not clearly
> possible.  There would be a hole fro. 8000 to 9FFF.   That's not great for
> CPM.
>
> Steve
>
> On Saturday, May 14, 2022, Hiraghm  wrote:
>
>> Is there an equivalent to the Model 100 REXCPM rom for the Model 200?
>>
>>
>>

Re: [M100] REXCPM for Model 200?

[Stephen Adolph]

Hi

At this time, no.   It would require some changes due to the unique memory
map in the T200 relative to the M100.

I think the biggest issue is that an all ram mode is not clearly possible.
There would be a hole fro. 8000 to 9FFF.   That's not great for CPM.

Steve

On Saturday, May 14, 2022, Hiraghm  wrote:

> Is there an equivalent to the Model 100 REXCPM rom for the Model 200?
>
>
>

[M100] REXCPM for Model 200?

[Hiraghm]

Is there an equivalent to the Model 100 REXCPM rom for the Model 200?