MPC562/MPC564 Compression Features
MPC561/MPC563 Reference Manual, Rev. 1.2
Freescale Semiconductor
A-11
A.2.9.5
Left Segment Bypass and Right Segment Compression—CLASS_4
This MPC562/MPC564 instruction is divided into two segments. The left segment is either fully bypassed
by a 16-bit field or by a shorter field which is decompressed according to fixed rules. The right segment
is compressed and mapped into a vocabulary. The vocabulary location is programmable. The compressed
fields must be swapped in the compressed instruction order to follow the rule that bypass appears only in
the second field of a compressed instruction.
.
Figure A-10. CLASS_4 Instruction Layout
The definition of the class includes:
•
TP1 length=2-9
•
TP2 length=0xB, 0xC, 0xD, or 0xE indicating a 0, 10, 15 or 16 bit bypass, respectively.
•
TP1 base address = base address of segment #1 vocabulary in RAM #1, if it exists there
•
TP2 base address = base address of segment #1 vocabulary in RAM #2, if it exists there
•
DS=1
•
AS=0 or 1 directing access to the vocabulary in RAM #1 or RAM #2, respectively.
When the vocabulary is located in RAM #1, the class is referred to as CLASS_4band when the vocabulary
is located in RAM #2, the class is referred to as CLASS_4a. Refer to
A.2.10
Instruction Layout Programming Summary
summarizes the programming for all possible compressed instruction layouts.
The un-compressed instruction of two half-words are referred as H1 & H2. The compressed instruction
can be built out of: (1) X1 field – representing a vocabulary pointer for encoding of either H1 or H1+H2;
(2) X2 field – representing a vocabulary pointer for encoding of H2; and (3) BP – representing a bypass
field.
Vocabularies V1 and V2 refer to the 16 MSB and 16 LSB of the uncompressed instruction, respectively.
A.2.11
Compression Process
The compression process is implemented by the following steps. See
•
User code compilation/linking
•
Vocabulary and class generation
•
User application code compression by a software compression tool
16-bit segment #1 – to be bypassed
2- to 9-bit TP1 for segment #2
4-bit class
Uncompressed Instruction
Compressed Instruction
16-bit segment #2 – to be compressed
MSB
0-, 10-, 15- or 16-bit bypass for segment #1
Summary of Contents for MPC561
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