FF7/Field/Script/Opcodes/79 MINUS2!

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Revision as of 01:40, 3 September 2006 by my_wiki>Halkun
  • Opcode: 0x79
  • Short name: MINUS2!
  • Long name: Saturated Subtraction (16-bit)

Memory layout

0x79 D/S Dest Oper

Arguments

  • const Bit[4] D: Destination bank
  • const Bit[4] S: Source bank
  • const UByte Dest: The destination variable, to which the operand is subtracted.
  • const SWord Oper: The operand to be subtracted from the destination.

Description

Subtracts "Oper" from "Dest" and stores the result back into "Dest". The result of the subtraction is capped at -32768. Oddly enough the result is not capped at the positive end, 32767, so subtracting a large negative number from a large positive number will still produce wrap-around. If the Source Bank is 0 then the “Oper” is subtracted from the destination value. If the Source Bank is an 16 bit bank, then the “Oper” is the address in that bank where the operand is.

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