Motorola MPC823e User Manual

Instruction Execution Timing
8-4 MPC823e REFERENCE MANUAL MOTOROLA
INSTRUCTION EXECUTION
8
TIMING
8.2 INSTRUCTION EXECUTION TIMING EXAMPLES
All examples assume an instruction cache hit.
8.2.1 Data Cache Load
lwz r12,64 (SP)
sub r3,r12,3
addic r4,r14,1
mulli r5,r3,3
addi r4,3(r0)
This is an example from a data cache with zero wait states. The sub instruction is dependent
on the value loaded by the load to r12. This causes a bubble to occur in the instruction
stream as shown in the execute line. Refer to Section 8.2.2.2 Private Writeback Bus Load
for instances in which no such dependency exists.
Figure 8-1. Example of a Data Cache Load
LWZ SUB MULLI ADDIADDIC
FETCH
DECODE
READ + EXECUTE
WRITEBACK
L ADDRESS DRIVE
L DATA
LOAD WRITE BACK
LWZ SUB
BUBBLE
ADD
ADDIC
LWZ SUB
SUB
ADDIC
LD
LD
LD

Motorola MPC823e Specifications

General

Brand	Motorola
Model	MPC823e
Category	Computer Hardware
Language	English