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Elite on the BBC Micro

Utility routines: DORND (6502SP version)

Name: DORND [View in context] Type: Subroutine Category: Utility routines Summary: Generate random numbers Deep dive: Generating random numbers
Set A and X to random numbers. The C and V flags are also set randomly. This is a simplified version of the DORND routine in the main game code. It swaps the two calculations around and omits the ROL A instruction, but is otherwise very similar. See the DORND routine in the main game code for more details.
.DORND LDA RAND+1 \ r1´ = r1 + r3 + C TAX \ r3´ = r1 ADC RAND+3 STA RAND+1 STX RAND+3 LDA RAND \ X = r2´ = r0 TAX \ A = r0´ = r0 + r2 ADC RAND+2 STA RAND STX RAND+2 RTS \ Return from the subroutine