Central Processing Unit
MPC561/MPC563 Reference Manual, Rev. 1.2
3-40
Freescale Semiconductor
3.13.3
Classes of Instructions
Non-optional instructions are implemented by the hardware. Optional instructions are executed by
implementation-dependent code and any attempt to execute one of these commands causes the RCPU to
take the implementation-dependent software emulation interrupt (offset 0x01000 of the vector table).
Illegal and reserved instruction class instructions are supported by implementation- dependent code and,
thus, the RCPU hardware generates the implementation-dependent software emulation interrupt. Invalid
and preferred instruction forms treatment by the RCPU is described under the specific processor
compliance sections.
3.13.4
Exceptions
Invocation of the system software for any instruction-caused exception in the RCPU is precise, regardless
of the type and setting.
3.13.5
Branch Processor
The RCPU implements all the instructions defined for the branch processor in the UISA in the hardware.
3.13.6
Instruction Fetching
The core fetches a number of instructions into its internal buffer (the instruction pre-fetch queue) prior to
execution. If a program modifies the instructions it intends to execute, it should call a system library
program to ensure that the modifications have been made visible to the instruction fetching mechanism
prior to execution of the modified instructions.
3.13.7
Branch Instructions
The core implements all the instructions defined for the branch processor by the UISA in the hardware.
For performance of various instructions, refer to
of this manual.
3.13.7.1
Invalid Branch Instruction Forms
Bits marked with z in the BO encoding definition are discarded by the MPC561/MPC563 decoding. Thus,
these types of invalid form instructions yield results of the defined instructions with the z-bit zero. If the
decrement and test CTR option is specified for the bcctr or bcctrl instructions, the target address of the
branch is the new value of the CTR. Condition is evaluated correctly, including the value of the counter
after decrement.
3.13.7.2
Branch Prediction
The core uses the y bit to predict path for pre-fetch. Prediction is only done for not-ready branch
conditions. No prediction is done for branches to the link or count register if the target address is not ready.
Refer to the
RCPU Reference Manual
(conditional branch control) for more information.
Summary of Contents for MPC561
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Page 144: ...Signal Descriptions MPC561 MPC563 Reference Manual Rev 1 2 2 46 Freescale Semiconductor...
Page 206: ...Central Processing Unit MPC561 MPC563 Reference Manual Rev 1 2 3 62 Freescale Semiconductor...
Page 302: ...Reset MPC561 MPC563 Reference Manual Rev 1 2 7 14 Freescale Semiconductor...
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Page 1144: ...Internal Memory Map MPC561 MPC563 Reference Manual Rev 1 2 B 34 Freescale Semiconductor...
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