T68KRC, 68000 SBC with I/O expansion bus compatible with RC2014 I/O bus
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Bill Shen
Jul 14, 2018, 8:32:17 PM7/14/18
to RC2014-Z80
A few people are interested in the progress of T68KRC so I'm starting a topic on it even though it is not quite ready for release. Here is the first picture of T68KRC, Tiny68K for RC2014. The design is derived from Tiny68K:
https://www.retrobrewcomputers.org/doku.php?id=boards:sbc:tiny68k
Instead of having 16meg of memory, T68KRC only has 2 meg of memory. Like Tiny68K, T68KRC has no parallel ROM. The boot ROM is a 32Kbyte serial flash that's copied into the lowest 32Kbyte of the memory when powered up or with a reset.
I've successfully built up one board and it booted and ran a modified version of the Tiny68K monitor. It runs OK at 8MHz but failed memory diagnostic intermittently at 12MHz. There is one known layout mistake with serial port hardware handshakes but that's easily corrected. CP/M ver 1.3 is running. I can access the few RC2014 I/O modules I have on hand. So things are working reasonably well, but there are a lot more tests to do and even more documentation to write.
More information about T68KRC can be found here. Information is added daily.
https://www.retrobrewcomputers.org/doku.php?id=builderpages:plasmo:t68krc
A near-term to-do list:
* Update the CP/M 1.3 BIOS for smaller RAMdisk,
* A new procedure for creating new CF disk,
* Test the CF interface against the collection of 20 different CF disks,
* Understand why it won't run at 12MHz reliably. The design should work up to 16MHz,
* Test for the various RC2014 I/O modules, special attention to the interrupt services of the RC2014 modules,
* Update the T68KRC wiki page.
Bill
https://www.retrobrewcomputers.org/doku.php?id=boards:sbc:tiny68k
Instead of having 16meg of memory, T68KRC only has 2 meg of memory. Like Tiny68K, T68KRC has no parallel ROM. The boot ROM is a 32Kbyte serial flash that's copied into the lowest 32Kbyte of the memory when powered up or with a reset.
I've successfully built up one board and it booted and ran a modified version of the Tiny68K monitor. It runs OK at 8MHz but failed memory diagnostic intermittently at 12MHz. There is one known layout mistake with serial port hardware handshakes but that's easily corrected. CP/M ver 1.3 is running. I can access the few RC2014 I/O modules I have on hand. So things are working reasonably well, but there are a lot more tests to do and even more documentation to write.
More information about T68KRC can be found here. Information is added daily.
https://www.retrobrewcomputers.org/doku.php?id=builderpages:plasmo:t68krc
A near-term to-do list:
* Update the CP/M 1.3 BIOS for smaller RAMdisk,
* A new procedure for creating new CF disk,
* Test the CF interface against the collection of 20 different CF disks,
* Understand why it won't run at 12MHz reliably. The design should work up to 16MHz,
* Test for the various RC2014 I/O modules, special attention to the interrupt services of the RC2014 modules,
* Update the T68KRC wiki page.
Bill
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