MPC555
/
MPC556
BURST BUFFER
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
4-11
An instruction in memory which will serve as the target of a branch will have a label
attached. The label provides the needed pointer to the other half of the branch target
instruction. The label token will be skipped in normal sequential operation. The label
has three parts. First, the label prefix character (which is skipped by the decompres-
sor). Second, a 5-bit pointer to the second half of the instruction. Third, a bit which in-
dicates the location of the second instruction half on the same line or the next line.
Figure 4-10 Extracting Direct Branch Target Address in the Decompressor
4.3.7 Compressed Address Format – Indirect Branches
Indirect branches use the regular two pointer format described above. The indirect
branch destination address is copied without any change from one of the following reg-
isters:
• LR
• CTR
• SRR0
See the PowerPC™
RCPU User’s Manual
, RCPURM/AD
, for more details.
4.3.8 Compression Process
The compression process is implemented by the following steps (See
• User code compilation/linking
• User application code compression by software compression tool.
The compiler will add a few simple “hooks” to the compiled code which will make com-
pression possible. Compiled code will be generated in the “elf” format for code
Instruction Code
Label token
Base
Address
Left Stream
Right Stream
1
0
0
Boundary Bit Field
0
0
0
11 12
1819
30 31
1
1
0
1
1
1
Label Format
Prefix Character
5-bit Pointer
Same / Next Line bit
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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