Maxim Integrated DS4830A Optical Microcontroller - Manual (Page 228)

DS4830A User’s Guide
228
SUB / SUBB src Subtract / Subtract with Borrow
Description:
Subtracts the specified src from the active accumulator (Acc) and returns the result back to
the active accumulator. The SUBB additionally subtracts the borrow (Carry Flag) which may
have resulted from previous subtraction. For the complete list of src specifiers, reference the
MOVE instruction. Because the source is limited to 8 bits, the PFX[n] register is used to
supply the high-byte of data for 16 bit sources.
Status Flags: C, S, Z, OV
SUB Operation:
Acc  Acc - src
Encoding:
15 0
f101 1010 ssss ssss
Example(s):
; Acc = 2345h to start, A[1]= 1250h
SUB A[1] ; Acc = 10F5h, C=0, S=0, Z=0, OV=0
SUB A[1] ; Acc = FEA5h, C=1, S=1, Z=0, OV=0
SUB A[2] ; A[2] =7FFFh
;
 Acc = 7EA6h; C=0, S=0, Z=0, OV=1
SUBB Operation:
Acc  Acc – (src + C)
Encoding:
15 0
f111 1010 ssss ssss
Example(s):
; Acc = 2345h, A[1]= 1250h, C=1
SUBB A[1] ; Acc = 10F4h, C=0, S=0, Z=0
SUBB A[1] ; Acc = FEA4h, C=1, S=1, Z=0
Special Notes:
The active accumulator (Acc) is not allowed as the src for these operations.