Routines
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CE0D: Multiply A By DE
Used by the routine at FlipSprite.
Multiplies A by DE.
Input
A The first number
DE The second number
Output
HL The product
Clear the product and count the bits.
MultiplyAByDE CE0D PUSH BC Stash BC on the stack.
CE0E LD HL,$0000 Set HL to 0000.
CE11 LD B,$08 Set B to 08.
Shift the product and add when the next bit is set.
MultiplyAByDE_Loop CE13 ADD HL,HL Double HL.
CE14 RLCA Jump to MultiplyAByDE_Next if the carry flag is not set.
CE15 JR NC,MultiplyAByDE_Next
CE17 ADD HL,DE Add DE to HL.
MultiplyAByDE_Next CE18 DJNZ MultiplyAByDE_Loop Jump to MultiplyAByDE_Loop until B is zero.
CE1A POP BC Restore BC from the stack.
CE1B RET Return.
View the equivalent code in;
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