Routines
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65D6: Generate Random Number
Used by the routines at GameLoop and ActionKill.
Returns a number from 00 up to, but not including, A.
The frame counter chooses how far to walk around that range.
Input
A Exclusive upper bound
Output
A The generated number
Mix the frame counter into a number below the limit in A.
GenerateRandomNumber 65D6 PUSH BC Stash BC on the stack.
65D7 LD C,A Store the exclusive upper bound in C.
65D8 LD A,($5C78) Load *FRAMES into B as the loop count.
65DB LD B,A
65DC LD A,C Restore the exclusive upper bound into A.
GenerateRandomNumber_Loop 65DD DEC A Decrease the walking value by one.
65DE JR NZ,GenerateRandomNumber_Next Jump to GenerateRandomNumber_Next if it has not wrapped past zero.
65E0 LD A,C Wrap back to the exclusive upper bound.
GenerateRandomNumber_Next 65E1 DJNZ GenerateRandomNumber_Loop Decrease the frame-count loop by one and loop back to GenerateRandomNumber_Loop until the count is zero.
65E3 DEC A Decrease the result by one so the range starts at 00.
65E4 POP BC Restore BC from the stack.
65E5 RET Return.
View the equivalent code in;
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