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2-6 PPC405 Core User’s Manual
2.3.2.1 Count Register (CTR)
The CTR is written from a GPR using mtspr. The CTR contents can be used as a loop count that is
decremented and tested by some branch instructions. Alternatively, the CTR contents can specify a
target address for the bcctr instruction, enabling branching to any address.
The CTR is in the user programming model.
Table 2-1. PPC405 SPRs
Function Register Access Page
Configuration CCR0
Privileged 4-11
Branch Control
CTR
User 2-6
LR
User 2-7
Debug
DAC1 DAC2
Privileged 8-9
DBCR0 DBCR1
Privileged 8-4
DBSR
Privileged 8-7
DVC1 DVC2
Privileged 8-10
IAC1 IAC2 IAC3 IAC4 Privileged 8-9
ICDBDR
Privileged 4-14
Fixed-point Exception XER
User 2-7
General-Purpose SPR
SPRG0 SPRG1 SPRG2 SPRG3 Privileged 2-9
SPRG4 SPRG5 SPRG6 SPRG7 User read, privileged write 2-9
USPRG0
User 2-9
Interrupts and Exceptions
DEAR
Privileged 5-13
ESR
Privileged 5-11
EVPR
Privileged 5-10
SRR0 SRR1
Privileged 5-9
SRR2 SRR3
Privileged 5-9
Processor Version PVR
Privileged, read-only 2-10
Storage Attribute Control
DCCR
Privileged 7-17
DCWR
Privileged 7-17
ICCR
Privileged 7-17
SGR
Privileged 7-17
SLER
Privileged 7-17
SU0R
Privileged 7-17
Timer Facilities
TBL TBU
Privileged, write-only 6-1
PIT
Privileged 6-4
TCR
Privileged 6-9
TSR
Privileged 6-8
Zone Protection ZPR
Privileged 7-14