STD -- Set Direction Flag

STD -- Set Direction Flag Opcode Instruction Clocks Description FD STD 2 Set direction flag so (E)SI and/or (E)DI decrement Operation DF = 1; Description STD sets the direction flag to 1, causing all subsequent string operations to decrement the index registers, (E)SI and/or (E)DI, on which they operate. Flags Affected DF = 1 Protected Mode Exceptions None Real Address Mode Exceptions None Virtual 8086 Mode Exceptions None