Routines
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C0D3: Update Random Numbers
Used by the routine at InitialiseGame.
Stirs the two random numbers in FirstRandomNumber and SecondRandomNumber. The first uses FrameCounter and the refresh register, and the second uses the frame counter and the return address, so it is different for every routine which calls this.
Stir the first random number with the frame counter and the refresh register.
UpdateRandomNumbers C0D3 LD DE,($A216) Fetch FrameCounter into DE.
C0D7 LD HL,($A218) Fetch FirstRandomNumber.
C0DA LD A,R Fetch the refresh register.
C0DC ADD A,E Add the low byte of the frame counter.
C0DD ADD A,L Add the low byte of the random number.
C0DE LD L,A Set the low byte of the new number.
C0DF LD A,R Fetch the refresh register again.
C0E1 ADD A,D Add the high byte of the frame counter.
C0E2 ADD A,H Add the high byte of the random number.
C0E3 LD H,A Set the high byte of the new number.
Store the first random number.
C0E4 LD ($A218),HL Set FirstRandomNumber.
Stir the second random number with the frame counter and the return address.
C0E7 POP BC Fetch the return address into BC, leaving it on the stack.
C0E8 PUSH BC
C0E9 LD HL,($A21A) Fetch SecondRandomNumber.
C0EC LD A,C Fetch the low byte of the return address.
C0ED SUB E Subtract the low byte of the frame counter.
C0EE ADD A,L Add the low byte of the random number.
C0EF LD L,A Set the low byte of the new number.
C0F0 LD A,B Fetch the high byte of the return address.
C0F1 SUB D Subtract the high byte of the frame counter.
C0F2 ADD A,H Add the high byte of the random number.
C0F3 LD H,A Set the high byte of the new number.
Store the second random number.
C0F4 LD ($A21A),HL Set SecondRandomNumber.
C0F7 RET Return.
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