Zilog Z08470 - Manual (Page 288)

Z80 Instruction Set UM008007-0715
276
Z80 CPU
User Manual
Condition Bits Affected
None.
Example
A typical software routine is used to demonstrate the use of the DJNZ instruction. This
routine moves a line from an input buffer (INBUF) to an output buffer (OUTBUF). It
moves the bytes until it finds a CR, or until it has moved 80 bytes, whichever occurs first.
LD 8, 80 ;Set up counter
LD HL, Inbuf ;Set up pointers
LD DE, Outbuf
LOOP: LID A, (HL) ;Get next byte from
;input buffer
LD (DE), A ;Store in output buffer
CP ODH ;Is it a CR?
JR Z, DONE ;Yes finished
INC HL ;Increment pointers
INC DE
DJNZ LOOP ;Loop back if 80
;bytes have not
;been moved
DONE: