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March 2002 Release
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Virtex-II Pro™ Platform FPGA Documentation
Appendix F:
PowerPC
®
Book-E Compatibility
R
Timer Resources
The PowerPC Book-E architecture modifies some aspects of the timer resources, as follows:
•
The architecture does not define a
move-from time base
(
mftb
) instruction. Software that
reads the time base must use a
move-from SPR
(
mfspr
) instruction with an SPR
number corresponding to the appropriate time-base register.
•
The programmable-interval timer (PIT) register is replaced by the decrementer (DEC).
These registers have different SPR addresses.
•
A DEC auto-reload mechanism is provided. This mechanism is more flexible than the
similar PIT auto-reload mechanism supported by the PowerPC 40x family.
•
The programmable-interval timer (PIT) interrupt is replaced by the decrementer
interrupt.
•
The timer-control register (TCR) controls different FIT and watchdog time-out
intervals, and it controls the decrementer instead of the PIT.
•
The timer-status register (TSR) describes decrementer status instead of PIT status.
Other Differences
Instructions
PowerPC 40x processors and PowerPC Book-E processors can support implementation-
specific instructions. For example, the multiply-accumulate (MAC) instructions are
considered implementation dependent and are not guaranteed to be supported by other
processors. Also, the PowerPC 440 processor supports the implementation-specific
determine left-most zero byte
(
dlmzb
) instruction. Refer to
, for a list of
implementation dependent PPC405 instructions. This table also shows which PPC405
instructions are not supported by the PowerPC Book-E architecture.
Debug Resources
Debug resources are implementation dependent. In general, all PowerPC 40x processors
and PowerPC Book-E processors support a common set of debug events on both
instruction addresses and data addresses. Debug events are controlled using the DBCR
n
registers. Debug status is reported by the DBSR register.
9
DIZ—Data and Instruction Storage, Zone
Protection
Reserved
10:11
Reserved
Implementation dependent
12
Program—Floating-Point Instruction
AP—Auxiliary-Processor Instruction
13
Program—Auxiliary-Processor Instruction
PUO—Unimplemented Operation
14
Reserved
BO—Byte Ordering
15
Reserved
Reserved
16
Data Storage—U0 Protection
17:23
Reserved
24:31
Reserved
Implementation dependent
Table F-8:
Comparison of ESR Bit Definitions
(Continued)
Bit
PowerPC 40x Function
PowerPC Book-E Function
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