MPC562/MPC564 Compression Features
MPC561/MPC563 Reference Manual, Rev. 1.2
A-16
Freescale Semiconductor
NOTE
The BBCMCR[DECOMP_SC_EN] bit determines if the data portion
(DATA[0:4]) of the instruction show cycle is driven or not, regardless of
decompression mode (BBCMCR[EN_COMP] bit)
A.3.2
Vocabulary Table Storage Operation
The MPC562/MPC564 uses DECRAM for decompressor vocabulary tables (VT1 and VT2) storage in
decompression on mode. The ICDU utilizes DECRAM as two separately accessed 1-Kbyte RAM arrays
(16 bits wide) that are accessed via internal ICDU buses. The VTs should be loaded before the
decompression process starts. In order to allow decompression, the DECRAM must be disabled for the
U-bus accesses after VTs and decompressor class configuration registers (DCCRs) are initialized.
A.3.3
READI Compression
Setting BBCMCR[DECOMP_SC_EN] when decompression is enabled allows READI to track the
compressed code (see
”). BBCMCR[DECOMP_SC_EN] should not be set
if there is no intention to use compressed code, as it will degrade U-bus performance. The show cycle may
be delayed by one clock by the USIU if the show cycle occurs after an external device read cycle. Refer
to
Section 24.6.5.2, “Compressed Code Mode Guidelines
The ICTRL register must be programmed such that a show cycle will be performed for all changes in the
program flow (ISCTL field = 0b01), or the PTM bit must be set and ISCTL must be set to a value other
than 0b11. (See
.)
A.3.3.1
I-Bus Support Control Register (ICTRL)
MSB
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Field
CTA
CTB
CTC
CTD
IWP0
IWP1
Reset
0000_0000_0000_0000
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
LSB
31
Field IWP2
IWP3
SIWP0
EN
SIWP1
EN
SIWP2
EN
SIWP3
EN
DIWP0
EN
DIWP1
EN
DIWP2
EN
DIWP3
EN
IFM ISCT_SER
1
1
Changing the instruction show cycle programming starts to take effect only from the second instruction after the
actual mtspr to ICTRL.
Reset
0000_0000_0000_0000
Addr
SPR 158
Figure A-13. I-Bus Support Control Register (ICTRL)
Summary of Contents for MPC561
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Page 144: ...Signal Descriptions MPC561 MPC563 Reference Manual Rev 1 2 2 46 Freescale Semiconductor...
Page 206: ...Central Processing Unit MPC561 MPC563 Reference Manual Rev 1 2 3 62 Freescale Semiconductor...
Page 302: ...Reset MPC561 MPC563 Reference Manual Rev 1 2 7 14 Freescale Semiconductor...
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Page 1144: ...Internal Memory Map MPC561 MPC563 Reference Manual Rev 1 2 B 34 Freescale Semiconductor...
Page 1212: ...TPU3 ROM Functions MPC561 MPC563 Reference Manual Rev 1 2 D 60 Freescale Semiconductor...
Page 1216: ...Memory Access Timing MPC561 MPC563 Reference Manual Rev 1 2 E 4 Freescale Semiconductor...