27C64 can't be used as-is.
pin 27 is A15 and needs to needs to go to a non-existing 2nd OE or CE.
You'd need an adapter board that combines pin 27 (A15) from the socket,
with pin 22 /CE0 (/BANK#1) from the socket, to produce a single /CE to
pin 22 of the chip.
You could do that with a single 2-gate NAND part the same as in this
model 200 RAM
https://github.com/bkw777/TANDY_200_RAM#single-bank---sop
https://raw.githubusercontent.com/bkw777/TANDY_200_RAM/main/TANDY_200_RAM.svg
That is using one nand gate just to invert /CS1 to CS1,
then ANDing those to make a single CS, and inverting that to make a
single /CS output to the chip's /CE
The point is getting the job done with only 2 gates of the same type so
it's all from a single part.
They even make little 8-leg parts with just the 2 needed gates.
For 27C64 you'd need to do that with /CE0 from bus pin 22 and CE1 from
bus pin 27, to produce a single /OE to chip pin 22. And chip pin 27
pulled to VCC by anything from 100k to a plain trace. All other pins
including /CS would go 1:1 socket to chip.
On 11/13/22 19:38, Mike Stein wrote:
Duh; shoulda looked more carefully; it really IS A15 (not A13) and it
goes to /CE1 (or CE1); double duh! Thanks, Brian.
So it looks like the only non-standard pin is pin 27, since 26 is not
used. Has anyone actually tried a JEDEC standard 27C64?
Pin 27 is the Program pin which looks like it might effectively be an
active high OE (since there is no program voltage.
m
On Sun, Nov 13, 2022 at 5:27 PM Brian White <[email protected]
<mailto:[email protected]>> wrote:
8k.
HN61364 = 8k
A15 is connected to a chip select to enable/disable the whole chip
(really just output enable not chip enable despite the /CEx labels),
and the actual address lines are only A0-A12
It's mostly like 27C64 but with 3 OE lines, customer programmable to
be either active high or low as part of the mask programming.
Although the schematic labels them as /CE0 /CE1 /CE2, really they
are all OE not CE, and it appears that /CE1 should be shown as
active-high, so really: /OE0, OE1, /OE2 , and /CS is a normal actual
whole chip enable, active low.
I was just now in the middle of drawing up an adapter for that chip
like FlexROM_102 but for that chip, to facilitate using the main rom
replacement feature of REX Classic in a 200 the way I have already
for 100 and 102.
But it may be simpler to make a different kind of adapter that
replaces both chips with a single larger chip on a single adapter in
the main rom socket and simply remove the 8k chip. The /BANK1 line
goes to both chips the same, and A15 ends up activating one or the
other exclusively at any given moment.
bkw
On Sun, Nov 13, 2022, 4:48 PM Mike Stein <[email protected]
<mailto:[email protected]>> wrote:
Looking at the schematic, are you sure it's 8K and not 16 (27x128)?
Looks standard except for pins 26 & 27
On Sun, Nov 13, 2022 at 4:23 PM Stephen Adolph
<[email protected] <mailto:[email protected]>> wrote:
Georg,
What type of ROM chips did you use, when you replaced your
ROMs with patched versions?
I've been pondering what the simplest way to do that is.
The 8K M13 socket is wired oddly, and doesnt seem compatible
with a 27C64.
thx
Steve
On Sun, Nov 13, 2022 at 12:30 PM Georg Käter
<[email protected]
<mailto:[email protected]>> wrote:
Hello together,
I own a M200 "German/EU Version" (Art.Nr. 26-3860H)
w/modem, for German market it was delivered with set of
keyboard
caps and a data tape including driver for keyboard and
printer. I tried this in VirtualT and it seems to work
so far. To run REX
on my M200 I replaced original ROM by ROM from VirtualT
patched to serve german keyboard mapping.
For your reference I´ve added original ROM files and
files from tape for your reference.
Regards
Georg
Georg Käter
Gangolfsweg 44
D-52076 Aachen
Tel. : +49 2408 7194987
Fax. : +49 2408 7196758
Mobil : +49 171 4839954
E-Mail :
[email protected]
<mailto:[email protected]>
========== Ihre Nachricht
==========================================
*von* : Cedric Amand <[email protected]
<mailto:[email protected]>>
*gesendet* : Sonntag, 13. November 2022, 15:37
*an* : [email protected]
<mailto:[email protected]>
*Betreff* : [M100] custom key mapping generator for
Tandy 200
__________ Originalnachricht
_______________________________________
My point exactly Brian !
How did they come up with that idea ? It makes no
sense. It really prevents you from using the option
rom socket.
The docs does not talk about removing it.
And even if you could remove it ; the installation
procedure of that ROM is not easy at all, requires
to type two "calls" with the freaking keyboard inverted.
OK - us nerds 40 years later can do it easily, just
type "CQLL", but imagine explaining that to a random
journalist in 1984 ?!
Especially as the french doc (which I happen to
have) says to type "CALL" not CQLL.
I also wonder if other markets are affected by this
plague,
If anyone here lives in germany and owns a qwertz
(or other keyboard variant) of the M200 : do you
have a "stock option ROM" as well ?
I also wish to thank Stephen publicly for the time
he invested into helping me, as indeed, you can't
use an option ROM (and even less a REX#) in those
non-qwerty M200s, and I think this research might
help some other people at some stage (this hobby is
booming right ? :) )
We're (and I am) in the process of replacing the
main rom + 8KB rom with a 27C512 flashed with a
custom "native Azerty" firmware
Which should free up to option socket, for a REX#
I also plan to make other modifications to that
custom ROM, but we'll see if I get there.
I've also been experimenting in the past with custom
firmware for the my M102 for different reasons.
I'm a "modem" nerd and I have all the equipment
(PABX, etc) to make voice calls between my vintage
laptops - so it's important for me to have my modems
work. This required a custom firmware to make my
M102 work, with modem, with a REX#. ( OK I think
this kind of stuff is only relevant to me this time
:) :)
Le 2022-11-13 14:53, Brian White
<[email protected] <mailto:[email protected]>>
a écrit :
Nice.
So the point would be to make the main rom
natively azerty to match the hardware, free up
the option rom slot for normal use, without
otherwise changing the main rom so that it
becomes incompatible with application software?
I guess you might even be able to make a dvorak
version and move the keycaps around?
I'm just trying to imagine the sales pitch for
that azerty 200 that needs the option rom, thus
preventing the use of any other option rom (or
at least making it pretty inconvenient by having
to swap them on every reset I guess?)
"Here's your new model 200. It's only half as
useful as others with no modem and no option rom
but you can still pay full price please."
--
bkw
On Sun, Nov 13, 2022, 8:28 AM Stephen Adolph
<[email protected]
<mailto:[email protected]>> wrote:
hi folks,
Thought I would share this work. It is a
spreadsheet for computing the keyboard table
in the T200 so you can make native custom
keyboards for T200.
Why?
The AZERTY keyboard in Europe was
accommodated using an option ROM that kinda
hacked the keyboard. Keystrokes get
intercepted and corrected to be AZERTY even
though the main ROM is set up for QWERTY.
An alternative is to have the main rom
directly support AZERTY.
To do this, there are 6 keyboard mapping
tables that start at 9763h. Each table are
44 bytes long.
This spreadsheet lets you assign the ascii
codes for each of the 44 affected keys, for
all 6 tables. (unshifted, shifted, GRAPH,
shift GRAPH, CODE, Shift CODE).
It is an excel spreadsheet that included the
analysis add it so that certain needed
functions are present.
Once you make the correct keyboard mapping,
the spreadsheet provides the 6x44 bytes in
assembly compatible form, so you can compile
and patch the tables with a hex editor.
This approach could be used for other
machines also.
Note - the AZERTY keyboard did NOT modify
the actual character set, so that is out of
scope. Of course it is possible to patch
the main ROM to change the bitmaps as well.
Not handled by this spreadsheet.
Comments welcome.
Steve
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