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Instruction Set
3-37
RISC 16−Bit CPU
* DEC[.W] Decrement destination
* DEC.B Decrement destination
Syntax DEC dst or DEC.W dst
DEC.B dst
Operation dst − 1 −> dst
Emulation SUB #1,dst
Emulation SUB.B #1,dst
Description The destination operand is decremented by one. The original contents are
lost.
Status Bits N: Set if result is negative, reset if positive
Z: Set if dst contained 1, reset otherwise
C: Reset if dst contained 0, set otherwise
V: Set if an arithmetic overflow occurs, otherwise reset.
Set if initial value of destination was 08000h, otherwise reset.
Set if initial value of destination was 080h, otherwise reset.
Mode Bits OSCOFF, CPUOFF, and GIE are not affected.
Example R10 is decremented by 1
DEC R10 ; Decrement R10
; Move a block of 255 bytes from memory location starting with EDE to memory location starting with
;TONI. Tables should not overlap: start of destination address TONI must not be within the range EDE
; to EDE+0FEh
;
MOV #EDE,R6
MOV #255,R10
L$1 MOV.B @R6+,TONI−EDE−1(R6)
DEC R10
JNZ L$1
; Do not transfer tables using the routine above with the overlap shown in Figure 3−12.
Figure 3−12. Decrement Overlap
EDE
EDE+254
TONI
TONI+254