Commstar 1.40 disassembly

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Commstar 1.40 disassembly

Post by johnkenyon » Fri Jul 13, 2018 4:51 pm

Here's my annotated disassembly of Commstar 1.40

Note that it's written to be assembled using the xa 6502/RC65C02/68516 cross-assembler.
For the uninitiated, this means:
1) $FF not &FF for hex
2) % indicates binary (used once)
3) ROR replaces ROR A, ROL replaces ROL A, and ASL replaces ASL A

To assemble:
xa whatever.asm -o whatever.hex

Hacker Short cuts:
"I want to hack the defaults"
TERMDEF - Terminal mode defaults
PRESDEF - Prestel mode defaults

"I want to implement a function assigned to a Fn key in chat mode"
$92F5 Terminal mode function key lookup table (F9, COPY does nothing)
$94BE Prestel mode function key lookup table (F4 and F6 keys do nothing...)
So to create a new function key, assemble custom code at $A000 onwards and then insert the address into the table.
(Make sure you pad out the image to 16k)

Hope this is useful

Commstar disassembly (text with CRLF line terminators)
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