STD              Set Direction Flag                  Flags: O D I T S Z A P C
Logic:    DF   1           (Decrement in string instructions)

STD sets the Direction Flag. No other flags are affected. Setting the
direction flag causes string operations to decrement SI and DI.

Operands                  Clocks   Transfers  Bytes   Example
no operands                 2          -        1     STD

See also: CLD
See also: STC
See also: CLC
See also: CMC
See also: STI
See also: CLI
See also: Flags

STD Set Direction Flag