RCA COSMAC VIP Instruction Manual
CHIP-8 User Notes
1Do 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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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.
