It's actually a very capable monitor ROM, including a full disassembler and a single stepper that uses 6522 interrupts.
Here's the ROM image (in ATM format):
Here's the original advert:
Program Power - Machine Code Monitor / Disassembler
- SINGLE STEP with REGISTER DISPLAY
- BREAKPOINT handling routines
- Tabulation Memory Dump with 'on-screen' Editing (printer option)
- Memory Display - Hex, ASCII, Screen Code, Decimal & Binary
- SEARCH - Hex or ASCII string
- INTELLIGENT COPY
- COMPARISON of two memory blocks
- DISASSEMBLER (full feature)
- INCREDIBLE PRICE - ONLY £14.95
Code: Select all
Code: Select all
"ESC" - exit to basic
":" - set low or high baud rate (H/L)
"P" - printer on
"O" - printer off
"R" - set current address
"M" - disassemble instruction at current address and increment
"N" - display contents of current address and increment
"-" - display contents of current address and increment
"COPY" - copy memory (to, from, end at)
"V" - verify memory (from, with)
"S" - search memory (from, to, for)
"H" - hex dump (from)
"T" - hex editor (cursor keys to move around, hex digits to edit, Q to quit)
"J" - jump to subroutine, allows screen swapping, single stepping, etc.
"I" - install a BRK handler and exit to Basic. Next BRK will be single stepped
"shift ^" - re-enter monitor (shift ^, next to BREAK)
When single stepping the registers can be modified with A, X, Y and P keys. And Q will stop single stepping.
The only other dedicated Monitor ROM I'm aware of for the Atom is the AEK Monitor ROM. This one is very good as well (I knew the author Alan Knowles), but it needs 1K of extra RAM from #9C00-#9FFF. If you know of any more Monitor ROMs, please let me know.