Register Model
PowerPC e500 Core Family Reference Manual, Rev. 1
Freescale Semiconductor
2-5
NOTE
The SPE APU and embedded floating-point APU functionality is
implemented in all PowerQUICC III devices. However, these
instructions will not be supported in devices subsequent to
PowerQUICC III. Freescale Semiconductor strongly recommends
that use of these instructions be confined to libraries and device
drivers. Customer software that uses SPE or embedded floating-point
APU instructions at the assembly level or that uses SPE intrinsics will
require rewriting for upward compatibility with next-generation
PowerQUICC devices.
Freescale Semiconductor offers a libmoto_e500 library that uses SPE
instructions. Freescale will also provide libraries to support
next-generation PowerQUICC devices.
This chapter describes how the e500 implements registers defined by Book E. As with the
instruction set and other aspects of the architecture, Book E defines some features very specifically,
for example, resources that ensure compatibility with implementations of the PowerPC ISA.
However, because a principal goal of the Book E architecture is to offer flexibility among embedded
processors and families of embedded processors, some resources are either defined as optional or
are defined in a very general way, leaving specific details up to the implementation.
2.2.1
Special-Purpose Registers (SPRs)
SPRs are on-chip registers that are architecturally part of the processor core. They control the use
of the debug facilities, timers, interrupts, memory management unit, and other architected
processor resources and are accessed with the mtspr and mfspr instructions. Unlisted encodings
are reserved for future use.
Table 2-1
summarizes SPRs defined in Book E. The SPR numbers are used in the instruction
mnemonics. Bit 5 in an SPR number indicates whether an SPR is accessible from user or
supervisor software. An mtspr or mfspr instruction that specifies an unsupported SPR number is
considered an invalid instruction. The e500 treats such invalid instructions as follows:
•
If the invalid SPR falls within the range specified as user mode (SPR[5] = 0), an illegal
exception is taken.
•
If supervisor software attempts to access an invalid supervisor-level SPR (SPR[5] = 1),
results are undefined.
•
If user software attempts to access an invalid supervisor-level SPR, a privilege exception is
taken.
Содержание PowerPC e500 Core
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