1 Oct
2023
1 Oct
'23
12:31 a.m.
Hi all
I re-discovered some eurocards I found in a box at a swapmeet long ago.
It looks like a complete 8085 system. Lots of RAM, 2K EPROM, I/O, FDC.
The strange thing is that the EPROM is mapped at F800, the code in there
looks like 8085 code, and looks like it wants to live at F800. And there's
RAM at 0000.
The DIN41612 A/C 64 pin bus has provision for 16 bits data.
Pics here http://retro.co.za/8085/Microcom/
Anyone maybe have more information on this? I'm curious.
W
1 Oct
1 Oct
12:45 a.m.
On Sun, Oct 1, 2023 at 8:38 AM Wouter de Waal via cctalk
<cctalk(a)classiccmp.org> wrote:
Hi all
I re-discovered some eurocards I found in a box at a swapmeet long ago.
It looks like a complete 8085 system. Lots of RAM, 2K EPROM, I/O, FDC.
The strange thing is that the EPROM is mapped at F800, the code in there
looks like 8085 code, and looks like it wants to live at F800. And there's
RAM at 0000.
It might have run CP/M (which will run on an 8080, and therefore on an
8085). That needs RAM at location 0000 [1].
If the EPROM is mapped to F800 only (some machines mapped it to 0000
as well after a reset, this image was disabled after the processor
jumped to F800 or wherever) then there might be a bit of logic to
force a jump instruction onto the data bus after a reset to get the
processor to run the code in the EPROM.
[1] For the pedants, there were 'relocated versions of CP/M that could
run on machines like an unmodified TRS-80 model 1 with ROM at location
0. These versions needed special relocated versions of all the
application software and were generally pretty useless.
-tony
3 Oct
3 Oct
6:46 a.m.
Wouter de Waal via cctalk wrote:
Hi all
I re-discovered some eurocards I found in a box at a swapmeet long ago.
It looks like a complete 8085 system. Lots of RAM, 2K EPROM, I/O, FDC.
The strange thing is that the EPROM is mapped at F800, the code in there
looks like 8085 code, and looks like it wants to live at F800. And there's
RAM at 0000.
The DIN41612 A/C 64 pin bus has provision for 16 bits data.
Pics here http://retro.co.za/8085/Microcom/
Anyone maybe have more information on this? I'm curious.
W
Besides of relocating the entire ROM temporarly to 0x0 there are other
possibilities, for example placing NOP's (0x0) on the data bus until
the bus addresses reaching 0xf800 for the first time. This way a few
extra gates and a flipflop is all what you need.
On Z80 Systems I've mostly used a mechanism that enables writes to the
RAM at 0x0, but the reads came from the ROM until an flipflop was set
by an out instruction (and reset by Reset).
Regards,
Holm
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2 comments
3 participants
participants (3)
-
Holm Tiffe -
Tony Duell -
Wouter de Waal