Routines
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32374: Prime pixel update
Sets up a call to 32362 ready to update a screen pixel according to the mode passed in here.
Select an entry from the jump table at 32366, copy the entry to the 2 bytes of storage at 32360. This primes the jump code at 32362 with A=0 31634 (set routine) A=1 31640 (clear) A=2 31647 (xor) A=3 31653 (clear byte)
Input
A 0 to 3, mode. 0=Set, 1=Clear, 2=XOR, 3=Clear byte
prime_update_pixel_trampoline 32374 PUSH HL Save regs
32375 PUSH BC
32376 AND 3 Bottom 2 bits only
32378 LD L,A HL = A
32379 LD H,0
32381 ADD HL,HL HL = Ax2
32382 LD BC,_UPDATE_PIXEL_JUMP_TABLE Jump table
32385 ADD HL,BC Select the entry from input value into HL
32386 LD BC,_UPDATE_PIXEL_TRAMPOLINE 2 byte result goes here
32389 LD A,(HL) Copy 2 bytes from jump table entry to result
32390 LD (BC),A
32391 INC HL
32392 INC BC
32393 LD A,(HL)
32394 LD (BC),A
32395 POP BC Restore regs
32396 POP HL
32397 RET
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