MPC555
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MPC556
BURST BUFFER
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
4-6
4.3.4 Memory Organization
In order to enhance performance, the logic is built to decode two halves of an instruc-
tion in parallel. The memory is arranged to support this as two streams of compressed
symbols: the left stream for the compressed symbols of X1 and X2 bytes, and the right
stream for the compressed symbols of X3 and X4 bytes.
Figure 4-4 Two Streams Memory Organization — Before Compression
In
, each left and right stream line includes two original bytes of the instruc-
tion.
, shows the memory after compressed streams have been put into it.
Figure 4-5 Two Streams Memory Organization — After Compression
X1, X2
X3, X4
31
0
15 16
Right Stream
Left Stream
Instruction
Code
Left Bit Pointer
Right Bit Pointer
Base
Address
Left Stream
Right Stream
1
0
0
Boundary Bit Field
0
0
0
1112
1819
30 31
1
1
0
1
1
1
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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