Routines
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748C: Make a sound effect
Used by the routines at 7118, 7414, 74C8, 7854 and 7EB1.
Input
A Initial border colour
B Pitch
C 0x10 + next border colour
DE Duration
748C PUSH HL
748D LD L,B Save the pitch parameter in L
748E OUT ($FE),A Flip the border colour and the state of the speaker
7490 XOR C
7491 LD B,L This is the pitch timing delay
7492 DJNZ $7492
7494 DEC E Jump back unless the sound effect is finished
7495 JR NZ,$748E
7497 DEC D
7498 JR NZ,$748E
749A LD A,$01 BORDER 1 (blue) before returning
749C OUT ($FE),A
749E POP HL
749F RET
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