LIST command initial work

i’ve decided to work on the LIST command rather than the hardware on the 8-bit project.  the LIST command shows a disassembly of several instructions, equivalent to the ‘L’ command in the apple 2 monitor.  so i’ve had some pretty good success this morning – i’m able to output the address and 3-letter opcode mnemonic.  no argument printing yet, but that’s next.

command format is

LIST [$xxxx]

as usual, the address argument is optional.  if omitted, listing will start at the address byte following the end of the previous LIST.  this allows the user, after an initial LIST command with address, to simply continue hitting return to show additional pages of disassembly.

output format for each line is

aaaa:  mmm   [args]

where ‘aaaa’ is the 4-hex-character address of the instruction, ‘mmm’ is the 3-character opcode mnemonic, and [args] is the arguments for the opcode as appropriate.  arguments will be displayed in the same format as the apple 2’s disassembly listing, e.g.” (zz),X” or “#$xx”.

since i’m using an LCD with 8 lines of text, only 7 lines of disassembly can be shown at once.  the eighth line is needed for the prompt for the next command line.

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