Motorola 24-Bit Digital Signal Processor, DSP56000 Absolute Value, Operation Assembler Syntax

INSTRUCTION DESCRIPTIONS

ABS	Absolute Value
Operation:	Assembler Syntax:

ABS

D ➞ D (parallel move) ABS D (parallel move)

Description: Take the absolute value of the destination operand D and store the result in the destination accumulator.

Example:
:
ABS A1 #$123456,X0 A,Y0	;take abs. value, set up X0, save value
:

A

Before Execution

$FF:FFFFFF:FFFFF2

A

After Execution

$00:000000:00000E

Explanation of Example: Prior to execution, the 56-bit A accumulator contains the value $FF:FFFFFF:FFFFF2. Since this is a negative number, the execution of the ABS instruction takes the twos complement of that value and returns $00:000000:00000E.

Note: For the case in which the D operand equals $80:000000:000000 (-256.0), the ABS instruction will cause an overflow to occur since the result cannot be correctly ex- pressed using the standard 56-bit, fixed-point, twos-complement data representation. Data limiting does not occur (i.e., A is not set to the limiting value of $7F:FFFFFF:FFFFFF).

Condition Codes:

15	14	13	12	11		10	9		8	7	6	5	4	3	2	1		0
LF	DM	T	**		S1	S0		I1	I0	S	L	E	U	N	Z		V	C
				MR									CCR

S — Computed according to the definition in A.5 CONDITION CODE COMPUTATION. L — Set if limiting (parallel move) or overflow has occurred in result

E — Set if the signed integer portion of A or B result is in use U — Set if A or B result is unnormalized

N — Set if bit 55 of A or B result is set Z— Set if A or B result equals zero

V — Set if overflow has occurred in A or B result

Note: The definitions of the E and U bits vary according to the scaling mode being used. Refer to Section A.5 for complete details.

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