Zilog Z8F0130 - Manual (Page 158)

eZ8
™
CPU Core
User Manual
UM012820-0810 DJNZ Instruction
143
Sample Usage
DJNZ typically controls a loop of instructions. In this example, 18 bytes
are moved from one buffer area in the Register File to another and the
steps involved are:
1. Load the R6 counter with 18d ( 12h ).
2. Load the R4 source pointer.
3. Load the R2 destination pointer.
4. Set up the loop to perform moves.
5. End loop with DJNZ.
The assembly listing required for this routine is as follows:
Ld R6, #12h ;Load counter with 12h (18d)
Ld R4, #36h ;Load source pointer
Ld R2, #24h ;Load destination pointer
LOOP: Ld R3, @R4 ;Load byte in R3 from source
Ld @R2, R3 ;Write byte to destination
dec R4 ;Decrement source pointer
dec R2 ;Decrement destination pointer
djnz R6, loop ;Decrement and loop until count =
0