8051 Instruction Set Manual

DJNZ

The DJNZ instruction decrements the byte indicated by the first operand and, if the resulting value is not zero, branches to the address specified in the second operand.

Note

When this instruction is used to modify an output port, the value used as the port data is read from the output data latch, not the input pins of the port.

See Also: CJNE

DJNZ
PC = PC + 2
(direct) = (direct) - 1
IF (direct) <> 0
  PC = PC + offset

DJNZ 40h, LABEL

DJNZ
PC = PC + 2
Rn = Rn - 1
IF Rn <> 0
  PC = PC + offset

DJNZ R6, LABEL