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Virtex-II Pro™ Platform FPGA Documentation
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should not rely on any initial values contained in those registers. The machine-
state register and several special-purpose registers have defined contents
following a reset. This enables the processor to quickly initialize the minimum
number of registers for proper instruction fetching and execution.
At the chip level, device control registers can be initialized to defined values
following a reset. However, the registers and their initial contents are
implementation-dependent.
Machine-State Register
Following a reset, the machine-state register (MSR) is cleared to 0x0000_0000.
lists the implication of reset on the processor state as controlled by
the MSR.
Special-Purpose Registers
shows the contents of the special-purpose registers (SPRs) that have
defined values following a reset. The contents of all other SPRs are undefined
after a reset.
Table 10-1:
MSR State Following Reset
MSR Bit
Value
Implication
AP
0
Auxiliary-processor unit unavailable.
APE
0
Auxiliary-processor unit exceptions disabled.
WE
0
Wait state disabled.
CE
0
Critical interrupts (external) disabled.
EE
0
Noncritical interrupts (external) disabled.
PR
0
Processor is in privileged mode.
FP
0
Floating-point unit unavailable.
ME
0
Machine-check exceptions disabled.
FE0
0
Floating-point exceptions disabled.
DWE
0
Debug-wait mode disabled.
DE
0
Debug exceptions disabled.
FE1
0
Floating-point exceptions disabled.
IR
0
Processor is in real mode (instruction translation is disabled).
DR
0
Processor is in real mode (data translation is disabled).
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