Micromon port to Planck 6502

Port of Floobydust's MicroMon 1.2 to Planck 6502

This is a port of the Micromon project created by Floobydust so that it will run on the Planck 6502 SBC. I'm making this port to learn more about 6502 assembly language and so there are bound to be errors or problems.

I've adapted the source code to compile using the ca65 assembler. I've replaced the "org" directives with the ".segment" command that ca65/ld65 seems to prefer. Other changes include replacing .db with .byte and .dw with .word.

I also added .PC02 to turn on support for 65C02 op codes and added .FEATURE labels_without_colons, which allows labels without colons. I also commented out the printing related items at the top of the file.

Because the Planck uses a WDC 65C51, which has a well-known transmit bug (search 6502.org for extensive discussions of the issue), it's not possible to use interrupt-driven data transmission. To work around this bug, I've substituted Floobydust's delay-based routines from the 6502.org for transmission; however, the receive function is still interrupt-driven and this may be something that can be ported back over to the Planck.

If you compile this for your Planck, you may want to adjust the ACIA_DELAY variable. My Planck is running with 1 wait state so I set the delay to 6 (representing a 6 Mhz processor speed). The ROM assumes that the user will connect at 19,200 N-8-1. If you change it to 115200, then you probably want to change the delay routine so that it consumes about 100 cycles per loop, rather than 600.

I've also included some basic shell scripts for building the bin file and for burning it to ROM.

Micro monitor functionality

The monitor packs a lot of functionality. Here is a list of the keys that can be used. In addition, the NMI button on the Planck will trigger a diagnostic save of computer data.

• [CNTRL-R] Reset
• ( Init Macro
• ) Run Macro
• A Display/Edit A register
• C Compare memory block
• D Display Memory contents in HEX/TEXT
• F Fill memory block
• G Go execute at
• H Hex byte string search
• M Move memory block
• P Display/Edit CPU status reg
• R Display Registers
• S Display/Edit stack pointer
• T Text character string search
• X Display/Edit X register
• Y Display/Edit Y register

Much more can be learned from studying the source code.

Again, I didn't create any of this. This is all great work by Floobydust, who made MicroMon and by Jonathan Foucher, who created the Planck computer