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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

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

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.