Concorde C-221M Disk Drive PSU?

[BeaglzNZ]

Rear of Concorde Drive:

 

[BeaglzNZ]

Atari Concorde C-221M ROM ver 1.2 - if not allowed to post here please delete.

 

As far as I know this has 'dumped' correctly - first time using my Eprom Programmer. No errors (or smoke) so should be all good!

Atari C-221M ver 1.2.BIN

[+Nezgar]

Thanks for dumping the ROM! Finally took a peek at the ROM dump today, and I dunno, I was surprised to see that there's only what looks like code for the first 1503 bytes, then FF's until the end of the first 2K. The second 2K is all 00's.

I guess, if Atari managed to squeeze the 810 code into 2K, and if Z80 code really is more compact to do more in less instructions (like driving extra external drives and double density) it's possible they could have done it in less than 2K. And by 1984 2732's were probably cheaper, and offered more upgrade potential vs a 2K EPROM.

Hopefully someone knowledgeable in Z80 disassembly can look at it and try to surmise something from it...

 

Edit: D'oh, Z8, not Z80!

[phaeron]

Managed to find a Z8 disassembler and disassemble the ROM. There's not much here:

• Command set is bare minimum 810 compatible: $52, $50, $57, $53, $21.
• Single-density only, no high speed support. FIrmware hardcoded to 40 track / 18 sectors / 128 bytes.
• Supports up to four drive mechanisms, but firmware appears hardcoded to allocate from D1: up.
• Get Status only returns bit 2 (unsuccessful PUT operation) in the first byte. FDC status byte is passed through, format timeout is $E2.
• UART is programmed for dead-on 19200 baud: 7.378MHz / 128 / 3 / 1. It is reprogrammable for different rates, but the low base clock means that the only other baud rates are 38.4K and 57.6K.
• Format sector order is 17, 15, ..., 1, 18, 16, ..., 2.
• Firmware is at $0000-07FF, RAM sector buffer is $1800-187F. The RAM setup is bizarre, there is a 1K static RAM on the board, but the firmware only uses 128 bytes of it, and can handle it being mapped to either $1800 or $1C00.