Commodore PET <-> CS/A65 bus adapter
This is the description of an adapter to use CS/A boards in a Commodore PET. A lot of CS/A boards, including a video card, serial interfaces, floppy controller and an SCSI card can be found on the CS/A65 homepage.
The interface itself is, in fact, pretty simple. It is a board that is plugged underneath the 6502 CPU of the PET. On the other side it provides a socket for a CS/A bus card. Two things have to be considered for the schematics:
- The PET only has two free memory areas, $9*** and $A***, so additional memory address lines have to be generated separately.
- The I/O area is pretty cramped. Especially when you look at the original I/O area address decoding: PIA1 is selected when A4 is high, PIA2 when A5 is high, VIA when A6 is high and CRTC when A7 is high - which means that on some addresses multiple chips are selected. Only $E80* is left open. So this area is used to map the control registers.
News:
- 2006-12-20 Published the board.
Table of content
Board revisions
Version: 1.1a
Status: prototype
Notes
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This board has been tested with a 8296 only. |
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It seems that the board requires a separate power supply. When POKEing data into the BIOS memory, it works when between pokes there is enough time (e.g. a PRINT statement), but misses some writes when not. |
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The layout could be better. In a 8296 it reaches over the main board power connector. I had to use a stack of 40-pin sockets underneath to reach the necessary height. |
Files
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petcsadesc-v1.1.txt |
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pet_csadapter-v1.1a.sch |
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pet_csadapter-v1.1a-sch.png |
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pet_csadapter-v1.1a.brd |
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pet_csadapter-v1.1a-brd.png |
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8296board.jpg(The original 8296 board) |
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8296board+drvio.jpg(The board with adapter and DRVIO board) |
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8296board+bios.jpg(The board with adapter and BIOS board) |
