Motorola MPC823e User Manual

Instruction Execution Timing
MOTOROLA MPC823e REFERENCE MANUAL 8-5
INSTRUCTION EXECUTION
8
TIMING
8.2.2 Writeback
8.2.2.1 WRITEBACK ARBITRATION
mulli r12,r4,3
sub r3,r15,3
addic r4,r12,1
The addic instruction is dependent on the mulli result. Since the single-cycle instruction
sub has priority on the writeback bus over the mulli and the mulli writeback is delayed one
clock and causes a bubble in the execute stream.
mulli r12,r4,3
sub r3,r15,3
addic r4,r3,1
Figure 8-2. Example of a Writeback Arbitration
Figure 8-3. Another Example of a Writeback Arbitration
MULLI SUB ADDIC
FETCH
DECODE
READ + EXECUTE
WRITEBACK
MULLI SUB
BUBBLE
ADD
ADDIC
MULLI SUB, MULLI
MULLI
ADDIC
SUB
GCLK1
MULLI SUB ADDIC
FETCH
DECODE
READ + EXECUTE
WRITEBACK
MULLI SUB
ADD
ADDIC
MULLI SUB, MULLI
MULLI
ADDIC
SUB
GCLK1

Motorola MPC823e Specifications

General

Brand	Motorola
Model	MPC823e
Category	Computer Hardware
Language	English