The destination operand is decremented by 2. The original contents are lost.
Status Bits
N:
Set if result is negative, reset if positive
Z:
Set if dst contained 2, reset otherwise
C:
Reset if dst contained 0 or 1, set otherwise
V:
Set if an arithmetic overflow occurs, otherwise reset
Set if initial value of destination was 08001 or 08000h, otherwise reset
Set if initial value of destination was 081 or 080h, otherwise reset
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
R10 is decremented by 2.
DECD R10 ; Decrement R10 by 2
; 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-2(R6)
DECD R10
JNZ L$1