On Wed, 26 Apr 2000 02:30:13 +0000, Maarten ter Huurne wrote:
>> There is no problem, I think. MSX standard is about IM1, right?
>I'm not sure what the standard says. But there are IM2 program on MSX. The
>question is how many and whether they can be modified to use IM1 instead.
Hummm... What is the way IM2 works? IM1 I know perfectly well, but I don't
know a lot about IM2. The information I have here is:
When Z80 is interrupted on mode 2, the external device must provide a one
byte data, which is placed with the value on register I, composing a 16 bit
number (the I register will be placed as the most significant byte) which
must points to a position in the address table (0000h, 0008h, 0010h, 0018h,
0020h, 0028h, 0030h, 0038h). The byte pointed and the following are placed
on PC. The Z80 will execute them the routine pointed by PC.
There is any external device to provide such "initial" byte?
>> Yes, but Z180 has trap... the AB180 has trap feature?
>It has. But a trap only works if the opcode is unused. So if they made a
>new instruction with that same opcode, trap won't work. There is a complete
>instruction map in the PDF file on their site, so someone could check
>whether the opcodes are free or not.
I think Ademir will do this... (-: I'll check with him later, or even check
the PDF if I have some time (which will be a little difficult... :-)
>That's not what I'm worried about.
>The problem is, if you do an "OUT (#20),A" and the upper bits are zero, the
>hardware outside of the processor will never see the OUT, because it is
>sent to the internal I/O ports. Also, writing the wrong values to the
>internal I/O ports may crash your system.
Well, one solution is: map all ports on something like: FFxxh... all
hardware will be seen as there. And a hardware always sets the upper byte
as FFh.
>> I'm waiting Ademir's answer. I talk to him by phone and he liked a lot
>> of the 20MIPS at 20Mhz idea... (-;
>Note that 20MIPS is the best case: it will only be reached if you use only
>1-byte instructions. But even with longer instructions this processor is
>likely to be quite fast.
It's almost RISC... /-: I thought it was RISC... But it's an impressive
mark, since on Z180 12MIPS is the best case... and for Z380, 10.5MIPS is
also on the best case.
Abra�OS/2, Daniel Caetano ([EMAIL PROTECTED])
...!m.tag
OS/2 Sites: http://www.quasarbbs.com/daniel/
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MSX Sites: http://www.fudeba.cjb.net/
Drawings: http://www.djgallery.tsx.org/
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