Maxim Integrated DS4830 Optical Microcontroller - Manual (Page 217)

DS4830 User’s Guide
217
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.