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Intel Pentium CPU Instruction Set Reference

STD instruction - Set Direction Flag

Code Mnemonic Description
FD STD Set DF flag


Sets the DF flag in the EFLAGS register. When the DF flag is set to 1, string operations decrement the index registers (ESI and/or EDI).

Operands Bytes Clocks
1 2 NP


ID unaffected DF sets
VIP unaffected IF unaffected
VIF unaffected TF unaffected
AC unaffected SF unaffected
VM unaffected ZF unaffected
RF unaffected AF unaffected
NT unaffected PF unaffected
IOPL unaffected CF unaffected
OF unaffected