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March 2002 Release
1-800-255-7778
Virtex-II Pro™ Platform FPGA Documentation
Chapter 4:
PPC405 Privileged-Mode Programming Model
R
encoded using a
split-field notation
. For more information, see
Simplified instruction mnemonics are available for the
mtspr
and
mfspr
instructions when
accessing certain SPRs. See
, for more information.
Device Control Register Instructions
The
device control register
are used to read and write the
device control registers (DCRs) using a GPR as a destination or source register. The DCR
number (DCRN) shown in the operand syntax column can be specified as a decimal or
hexadecimal value in the assembler listing. Within the instruction opcode, this number is
encoded using a
split-field notation
. For more information, see
Processor Wait State
Software-controlled power management is possible through the use of the processor
wait
state
. Wait state is a low-power operating mode that can be used to conserve processor
energy when the processor is not busy. Wait state is entered when software sets the
wait-
state enable
bit (MSR[WE]) to 1.
When in the wait state, the processor stops fetching and executing instructions, and no
longer performs memory accesses. The processor continues to respond to interrupts, and
can be restarted through the use of external interrupts or timer interrupts. Wait state can
also be exited when an external debug tool clears WE or when a reset occurs.
Table 4-6:
Special-Purpose Register Instructions
Mnemonic
Name
Operation
Operand
Syntax
mfspr
Move from Special Purpose Register
r
D is loaded with the contents of the SPR specified
by SPRN.
r
D,SPRN
mtspr
Move to Special Purpose Register
The SPR specified by SPRN is loaded with the
contents of
r
S.
SPRN,
r
S
Table 4-7:
Device Control Register Instructions
Mnemonic
Name
Operation
Operand
Syntax
mfdcr
Move from Device Control Register
r
D is loaded with the contents of the DCR specified
by DCRN.
r
D,DCRN
mtdcr
Move to Device Control Register
The DCR specified by DCRN is loaded with the
contents of
r
S.
DCRN,
r
S