Motorola MPC533 Reference Manual page 1044

Class-Based Compression Model Main Principles
Alternatives #1 and #2 are referred to as CLASS_2a and CLASS_2b respectively.
0.0.0.1 Left Segment Compression and Right Segment Bypass –
CLASS_3
For the , the instruction is divided into two segments. The left segment is compressed and
mapped into a vocabulary. The vocabulary location is programmable. The right segment is
either fully bypassed by a 16-bit field or by a shorter field which is decompressed according
to fixed rules.
.
Msb
16-bit segment #1 – to be compressed
2- to 9-bit TP1 for segment #1
4-bit class
The definition of the class includes
• TP1 length=2-9
• TP2 length=11, 12, 13 or 14 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=0
• 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 will be referred to as CLASS_3a and
when the vocabulary is located in RAM #2, the class will be referred to as CLASS_3b.
G.2.9.4 Left Segment Bypass and Right Segment Compression –
CLASS_4
This 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
G-12
PRELIMINARY—SUBJECT TO CHANGE WITHOUT NOTICE
Uncompressed Instruction
16-bit segment #2 – to be bypassed
Compressed Instruction
Figure G-9. CLASS_3 Instruction Layout
MPC533 Reference Manual
0-, 10-, 15- or 16-bit bypass for segment #2
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