Motorola DSP56000, 24-Bit Digital Signal Processor manual Three-Stage Pipeline

PROGRAM CONTROL UNIT (PCU) ARCHITECTURE

	EXAMPLE PROGRAM SEGMENT
Instruction 1	MACR	X0,Y1,A	X:(R0)+,X0	Y:(R4)+,Y1
Instruction 2	CLR	A	X0,X:(R0)+	A,Y:(R4)-
Instruction 3	MAC	X0,Y1,A	X:(R0)+,X0	Y:(R4)+,Y1

PARALLEL PROCESSING OF INSTRUCTIONS

SEQUENCE OF OPERATIONS

SERIAL EXECUTION OF INSTRUCTIONS

Instruction Cycle 2

Instruction Cycle 3

Instruction

Cycle

Instruction Cycle 5

Instruction Cycle 1

INSTRUCTION

INSTRUCTION

INSTRUCTION

INSTRUCTION

INSTRUCTION

Instruction/Data Fetch

FETCH

FETCH

FETCH

FETCH

FETCH

LOGIC

LOGIC

LOGIC

LOGIC

4

LOGIC

5

1

2

3

INSTRUCTION

INSTRUCTION

INSTRUCTION

INSTRUCTION

DECODE

DECODE

DECODE

DECODE

Instruction Decode

LOGIC

LOGIC

LOGIC

LOGIC

1

2

3

4

INSTRUCTION

INSTRUCTION

INSTRUCTION

EXECUTION

EXECUTION

EXECUTION

Instruction Execution

LOGIC

LOGIC

2

LOGIC

3

1

EXECUTION OF EXAMPLE PROGRAM

		Instruction Cycle 1 Instruction Cycle 2 Instruction Cycle 3 Instruction Cycle 4 Instruction Cycle 5
INSTRUCTION FETCH		I1	I2	I3	I4	I5
INSTRUCTION DECODE			I1	I2	I3	I4
INSTRUCTION EXECUTION				I1	I2	I3
PARALLEL	INITIAL
OPERATIONS	CONDITIONS
ADDRESS
UPDATE	R0=$0005			R0=5+1	R0=6+1	R0=7+1
(AGU)	R4=$0008			R4=8+1	R4=9–1	R4=8+1
INSTRUCTION	A:			A:	A:	A:
	A2=$00			A2=$00	A2=$00	A2=$00
EXECUTION	A1=$000066			A1=$0000A2	A1=$000000	A1=$000000
	A0=$000000			A0=$000000	A0=$000000	A0=$000050
(DATA ALU)	X0=$400000			X0=$000005	X0=$000005	X0=$000007
	Y1=$000077			Y1=$000008	Y1=$000008	Y1=$000008
X MEMORY	DATA
AT ADDRESS
$0005	$000005			$000005	$000005	$000005
$0006	$000006			$000006	$000005	$000005
$0007	$000007			$000007	$000007	$000007
Y MEMORY	DATA
AT ADDRESS	$000008
$0008				$000008	$000008	$000008
$0009	$000009			$000009	$0000A2	$0000A2

Figure 5-3 Three-Stage Pipeline

MOTOROLA PROGRAM CONTROL UNIT 5 - 7