Motorola DSP56000 manual Signed Multiply-Accumulate and Round Macr, Condition Codes

INSTRUCTION DESCRIPTIONS

MACR

Signed Multiply-Accumulate and Round MACR

Explanation of Example 1: Prior to execution, the 24-bit X0 register contains the value $123456 (0.142222166), the 24-bit Y0 register contains the value $123456 (0.142222166), and the 56-bit B accumulator contains the value $00:100000:000000 (0.125). The execution of the MACR X0,Y0,B instruction multiples the 24-bit signed value in the X0 register by the 24-bit signed value in the Y0 register, adds the resulting product to the 56-bit B accumulator, rounds the result into the B1 portion of the accumu- lator, and then zeros the B0 portion of the accumulator (X0∗Y0+B=0.145227144519197 approximately =$00:1296CD:9619C8, which is rounded to the value $00:1296CE:000000=0.145227193832397=B).

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.

Instruction Format 1:
MACR		(±)S1,S2,D
MACR		(±)S2,S1,D
Opcode 1:
23	8	7	4	3	0
		DATA BUS MOVE FIELD	1 Q Q	Q	d k	1 1
		OPTIONAL EFFECTIVE ADDRESS EXTENSION

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