mpc823rg Freescale Semiconductor, Inc, mpc823rg Datasheet - Page 187

• Manufacturer Part Number: mpc823rg
• Description: Mpc823 Powerquicc Integrated Communications Processor For Portable Systems
• Manufacturer: Freescale Semiconductor, Inc

8.2.5 Branch Folding
lwz
sub
addic r4,r14,1
bl
...
func:
mulli r5,r3,3
addi r4,3(r0)
The lwz instruction accesses the internal storage with one wait state. The instruction
prefetch queue and parallel operation of the branch unit allows the two bubbles caused by
the bl issue and execution to overlap the two bubbles caused by the load. The issue of the
branch itself is referred to as a bubble since no actual work is done by a branch.
FETCH
DECODE
READ + EXECUTE
WRITEBACK
L ADDRESS DRIVE
L DATA
LOAD WRITEBACK
BRANCH DECODE
BRANCH EXECUTE
GCLK1
r12,64 (SP)
r3,r12,3
func
LWZ
Freescale Semiconductor, Inc.
Figure 8-7. Example of Branch Folding
For More Information On This Product,
LWZ
MPC823 REFERENCE MANUAL
SUB
LWZ
Go to: www.freescale.com
LWZ
SUB
ADDIC
BUBBLE
BL
BUBBLE
LWZ
BL
LWZ
BUBBLE
BL
SUB
Instruction Execution Timing
ADDIC
MULLI
SUB
ADDIC
MULLI
ADD
ADDI
MULLI
8-9