On Wed, 26 Apr 2000 03:55:22 +0000, Maarten ter Huurne wrote:
>> There is any external device to provide such "initial" byte?
>No, not on MSX.
>On most MSX machines the value "from the device" is #FF. But there have
>been cases reported of other values. The only safe way is to make code that
>works with any value (this is possible and has been discussed here before).
>Anyway, this new processor will always call #0038, even if the program
>requested IM2. It is very unlikely that that will work, since a programmer
>wouldn't go through the trouble of setting up IM2 if he want #0038 to be
>called.
I think there is a workaround. It has both interruptions like IM1 and IM2,
but are not modes. Once MSX has only one IRQ pin, you have to switch modes.
On AB180 you have 3 IRQ pins (note, I'm not talking about NMI). The workaround
is place a circuit before the processor to intercept IM1,IM2 instructions and
change where the IRQ goes, to pin IRQ0 (IM1) or IRQ1/2 (IM2).
>That still doesn't solve it.
>Example:
> LD BC,#2310
> OUT (C),A
>This will send A to I/O port #10 (high byte #23 ignored)
> LD BC,#0010
> OUT (C),A
>This will send A to internal I/O port #10 (high byte is zero).
>So the processor internal I/O port is written, not the MSX I/O port.
I see. Well, anyway, I'd talked to Ademir and he said this works on
the same way as Z180, and is possible to avoid it, because the internal
registers ports can be shifted...
>RISC is a kind of instruction set.
>Anything Z80 compatible can never be RISC.
R800 is. (-; Or, at least, It's written on MSX Turbo R box!
Abra�OS/2, Daniel Caetano ([EMAIL PROTECTED])
...!m.tag
OS/2 Sites: http://www.quasarbbs.com/daniel/
http://www.geocities.com/SiliconValley/8752/os2hp/os2index.html
MSX Sites: http://www.fudeba.cjb.net/
Drawings: http://www.djgallery.tsx.org/
****
MSX Mailinglist. To unsubscribe, send an email to [EMAIL PROTECTED]
and put "unsubscribe msx [EMAIL PROTECTED]" (without the quotes) in
the body (not the subject) of the message.
Problems? contact [EMAIL PROTECTED]
More information on MSX can be found in the following places:
The MSX faq: http://www.faq.msxnet.org/
The MSX newsgroup: comp.sys.msx
The MSX IRC channel: #MSX on Undernet
****
