MPC555
/
MPC556
BURST BUFFER
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
4-10
branch has nine bits. This will yield a conditional branch displacement limit of two
Kbytes.
When a change of flow occurs, the sequencer of the PPC core will issue the new ad-
dress in compression mapped format. The address extractor unit of the BBC gener-
ates the direct branch address format to internal memory.
Indirect branches use the regular two pointer format described in the previous section.
Figure 4-9 Generating Compressed Code Address
for PowerPC Direct Branches
0
6
Base Address of the
25
25
30 31
Word Pointer from
30 31
30 31
30 31
27
31
0
25
6
16
16
0
0
0
Unconditional immediate branch instruction BEFORE compression mapping
Unconditional immediate branch instruction AFTER compression mapping (I-form)
Conditional immediate branch instruction BEFORE compression mapping
Conditional immediate branch instruction AFTER compression mapping (B-form)
Direct (internal) branch address format (one pointer format)
5-biit
Pointer
5-bit
Pointer
5-bit
Pointer
Word Pointer
Word Pointer - Base Address
Word Pointer
Word Pointer
Word Pointer
Branch Instruction
the Immediate Field
Calculator
Base Address
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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