Motorola 24-Bit Digital Signal Processor, DSP56000 manual Subtract Long with Carry, Sbc

INSTRUCTION DESCRIPTIONS

	SBC	Subtract Long with Carry		SBC
Operation:			Assembler Syntax:
	D–S–C ➞ D (parallel move)		SBC	S,D (parallel move)

Description: Subtract the source operand S and the carry bit C of the condition code register from the destination operand D and store the result in the destination accumula- tor. Long words (48 bits) may be subtracted from the (56-bit) destination accumulator.

Note: The carry bit is set correctly for multiple-precision arithmetic using long-word oper- ands if the extension register of the destination accumulator (A2 or B2) is the sign exten- sion of bit 47 of the destination accumulator (A or B).

Example:

:

MOVE L:<$0,X MOVE L:<$1,A MOVE L:<$2,Y SUB X,A L:<$3,B SBC YB A10,L:<$4 MOVE B10,L:<$5

:

		Before Execution
A
	$00:000000:000000

;get a 48-bit LS long-word operand in X ;get other LS long word in A (sign ext.) ;get a 48-bit MS long-word operand in Y ;sub. LS words; get other MS word in B ;sub. MS words with carry; save LS dif. ;save MS difference

		After Execution
	$00:800000:000000
A

X

$800000:000000

X

$800000:000000

B

$00:000000:000003

B

$00:000000:000001

Y

$000000:000001

Y

$000000:000001

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