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BIOS and Monitor

A project log for HD6309 Singleboard Computer

Hitachi HD63C09 clocked at a blistering 3 MHz with a capacious 64K of RAM! Retroputing bliss...

tomcircuittomcircuit 03/31/2014 at 03:450 Comments

I've been working for a while on a BIOS for this SBC. I'm shooting for a compromise between flexibility and simplicity. I don't have any visions for direct compatibility with older systems (e.g. SWTPC 6809) so I'm not constrained in that respect. I figure that some set of services, accessed via SWI, that cover character I/O and hardware abstraction (RTC, CIO) will suffice. It's a work in progress, which as soon as I get something reasonably complete I'll put up on GitHub.

The monitor is a different story. I've been using the wonderful MON09 from Dave Dunfield (DDS). It's not open source, so I cannot share it, otherwise i would. It's very nice - breakpoints, disassembler, S19 and ihex loading, etc. I extended it to add support for the peripherals on the hd6309 SBC, such as the CIO, the RTC, and of course the SCC. Aside from the open source, it's not a real 6309 monitor - so it cannot disassemble the 6309 opcodes, for example. So, I'm moving towards porting the venerable ASSIST09 monitor to this hardware. It's not as nice as the DDS monitor, and STILL not 6309-aware. So, if anyone knows of a real 6309 ROM monitor, please let me know! I'd rather not reinvent the wheel.

Finally, I cannot believe how long I managed to not stumble across the NoICE debugger tools. This is a PC based remote debugger that interacts with a small debug client on the target hardware. It provides source-level debugging on the PC side. This seems to be a perfect fit for my needs. The second SCC serial channel can be used for a dedicated debug interface (PC side seems to top out at 115.2kbps, otherwise I'd go faster) so it doesn't hog up the terminal I/O channel. As I get that integrated into the monitor and BIOS suite, I'm sure I'll have more to say on this. Best of all, the 6309 and 6809 NoICE debugger tools are FREE if you send the author a short email telling him about your project. I got a reply back within a day, and a free license for the 6309 debug package. Nice!

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