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432
March 2002 Release
1-800-255-7778
Virtex-II Pro™ Platform FPGA Documentation
Chapter 4:
PPC405 Privileged-Mode Programming Model
R
The initial state of the MSR following a processor reset is described in
SPR General-Purpose Registers
The SPR general-purpose registers (SPRG0–SPRG7) are 32-bit registers that can be used for
any purpose by system software running in privileged mode. The values stored in these
registers do not affect the operation of the PPC405 processor.
Four of the registers (SPRG4–SPRG7) are available from user mode with
read-only access
.
Application software can read the contents of SPRG4–SPRG7, but cannot modify them.
The format of all SPRG
n
registers is shown in
17
PR
Privilege Level
0—Privileged mode.
1—User mode.
Controls the privilege level of the processor. See
, for more information.
18
FP
Floating-Point Available
(Unsupported)
This bit is unsupported and ignored by the PPC405D5. Software
should clear this bit to 0.
19
ME
Machine-Check Enable.
0—Disabled.
1—Enabled.
Controls the machine-check interrupt. See
, for more information.
20
FE0
Floating-Point Exception-Mode 0
(Unsupported)
This bit is unsupported and ignored by the PPC405. Software
should clear this bit to 0.
21
DWE
Debug Wait Enable
0—Disabled.
1—Enabled.
Controls the debug wait mode. See
for more information.
22
DE
Debug Interrupt Enable
0—Disabled.
1—Enabled.
Controls the debug interrupt. See
, for more information.
23
FE1
Floating-Point Exception-Mode 1
(Unsupported)
This bit is unsupported and ignored by the PPC405D5. Software
should clear this bit to 0.
24:25
Reserved
26
IR
Instruction Relocate
0—Instruction-address transla-
tion is disabled.
1—Instruction-address transla-
tion is enabled.
Controls instruction-address translation. See
, for more information. When address
translation is disabled, the processor is running in real mode. See
, for an introduction.
27
DR
Data Relocate
0—Data-address translation is
disabled.
1—Data-address translation is
enabled.
Controls data-address translation. See
, for more information. When address translation is
disabled, the processor is running in real mode. See
, for an introduction.
28:31
Reserved
Table 4-1:
Machine-State Register (MSR) Bit Definitions
(Continued)
Bit
Name
Function
Description
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