| Simple 68020 [message #4745] |
Thu, 07 June 2018 09:35  |
jbforrer
Messages: 25
Registered: May 2017
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Junior Member |
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Greetings,
Finally got to play with a 68020 after finding a design by Bas de Jong, a Dutch Ham Radio enthusiast.
This a very basic, but functional layout constructed on a piece of RS perfboard. All point-to-point soldered.
Runs stable at 20MHz with no wait states. 1MB SRAM wired 16-bit (55ns), 27C256 EPROM (55ns) and 68681 DUART for console I/O.
The 16V8B GAL (7ns) does address decoding, 8/16-bit bus access, and some glue logic. Otherwise, the usual RESET/HALT circuit and clock oscillators.
The MC68020RP16E is clocked at 20MHz and are stable. A modified version of a 68K monitor originally developed by Antonakos is in EPROM.
The board draws some 400mA, perhaps may run off USB power.
Further hardware and code development remains, but a modest beginnings.
Trust this is of interest.
Cheers.
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