Chip-8 User Notes - RCA CDP18S711 Instruction Manual

CHIP-8 User Notes

1 Do not use any of the CDP1802 three-cycle
machine language instructions in CHIP-8
programs.
2. CDP1802 R5 is used as the CHIP-8 instruction
counter. It will he addressing the byte following a
0MMM instruction for machine language
subroutines and can be used to pass 2-byte
parameters. Refer to the operating system register
table in Appendix B to examine this register during
CHIP-8 program debugging.
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RCA COSMAC VIP Instruction Manual
5. R7, RC, RD, RE, and RF can be used as
working registers in machine language
subroutines. Changing other registers can cause
the CHIP-8 interpreter to malfunction.
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7. Program bugs can destroy the CHIP-8 in-
terpreter at locations 0000-01FF. If you suspect
that this has happened, reload the interpreter.
8. The CHIP-8 interpreter uses subroutines and
digit patterns contained in the operating system
ROM. If you modify this operating system, the
CHIP-8 interpreter should not be used.