AMCC PPC405 - Count Register (CTR); Figure 2-4. Count Register (CTR); Table 2-1. PPC405 Sprs

AMCC Proprietary 36
Revision 1.02 - September 10, 2007
PPC405 Processor
Preliminary 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 77
Branch Control
CTR
User 36
LR
User 37
Debug
DAC1 DAC2
Privileged 147
DBCR0 DBCR1
Privileged 143
DBSR
Privileged 145
DVC1 DVC2
Privileged 147
IAC1 IAC2 IAC3 IAC4 Privileged 147
ICDBDR
Privileged 80
Fixed-point Exception XER
User 37
General-Purpose SPR
SPRG0 SPRG1 SPRG2 SPRG3 Privileged 39
SPRG4 SPRG5 SPRG6 SPRG7 User read, privileged write 39
USPRG0
User 39
Interrupts and Exceptions
DEAR
Privileged 118
ESR
Privileged 116
EVPR
Privileged 116
SRR0 SRR1
Privileged 115
SRR2 SRR3
Privileged 115
Processor Version PVR
Privileged, read-only 39
Storage Attribute Control
DCCR
Privileged 106
DCWR
Privileged 106
ICCR
Privileged 107
SGR
Privileged 107
SLER
Privileged 107
SU0R
Privileged 107
Timer Facilities
TBL TBU
Privileged, write-only 130
PIT
Privileged 131
TCR
Privileged 135
TSR
Privileged 135
Zone Protection ZPR
Privileged 103
Figure 2-4. Count Register (CTR)
0:31 Count
Used as count for branch conditional with
decrement instructions, or as address for branch-
to-counter instructions.