CS/A65 BIOS
This board implements basic memory and I/O functionality
for the CS/A65 computer.
The BIOS board complements the MMU CPU board in that it provides
some RAM, ROM, and basic I/O (a RS232 interface, that is).
It also has a special I/O port that allows the CPU to read the IRQ line,
or the state of a pushbutton. Also a 50 Hz interrupt is provided that
can be switched on and off with this port, as well as a system LED.
The I/O mapping can be changed from the BIOS port as well.
The older version 1 used a 6551 ACIA for the RS232 interface, but now I
use a 16550 UART (with FIFO).
Status: ok
Notes
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This is the new version of the board,
using larger (up to 512k) RAM and ROM sockets.
For this board also Eagle(tm) schematics and layout
files are available
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The RS232 functionality works, although it
seems larger capacitors for the RS232 voltage generation
could be needed, as my test board looses characters.
The same schematics works fine in the Gecko board,
though.
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The TTL parts mainly consist of the 'ALS (advanced
Low-Power Shottky) TTL types, except where available.
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Files
Status: ok
Notes
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This is the old version of the board,
using small (up to 32k) RAM and ROM sockets.
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Files
Status: ok
Notes
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This is the very first version, using an ACIA
for the serial interface. It is (here) only
documented as a photo.
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Files
This diagram shows an overview on the board architecture
