6502 Help References included in 6502 monitor

6502 mini-assembler help system

The help system recently added to the 6502 monitor (vwas6502) includes

• help commands
• monitor commands reference
• 6502 instruction set mnemonics
• 6502 addressing modes references, listing valid instructions
• opcodes with addressing modes available for a specific instruction mnemonic

In observation, that required a bit of ROM memory.  The monitor is currently at 4K with minimal features.  It is bursting at the seems without further space optimization, so will need to expand to 8K with the next feature additions.

Help commands

Monitor commands reference

6502 instruction set

6502 addressing modes

Help for a specific instruction

The references are possible, because the mini-assembler and disassembler is table driven.  There is a table of instructions in alphabetical order, an alphabetical index of the addressing modes, a table of addressing modes and an example for each in parsing (and number of bytes required) order, and tables of the opcodes: (ordered by) byte values, index to instruction name, and index to addressing mode.

By using the alphabetical indexes, the information can be displayed sorted when applicable.  This makes the information more easily accessible.

The 6502 specific references are generated by 6502 code on demand from the tables.  The commands reference and help about help are the only static help pages.  It would probably take a lot more storage if all the references were static, especially considering there are 56 separate instructions.

More information about this monitor is available in the previous article.