Central Processing Unit
MPC561/MPC563 Reference Manual, Rev. 1.2
Freescale Semiconductor
3-43
When the operand falls in the range of double denormalized numbers it is considered a programming error.
The hardware will handle this case as if the operand was ZERO.
The following check is done on the stored operand in order to determine whether it is a denormalized
single-precision operand and invoke the floating-point assist interrupt handler:
(frS[1:11]
≠
0) AND (frS[1:11]
≤
896)
Eqn. 3-1
Refer to the
RCPU Reference Manual
(Floating-Point Assist for Denormalized Operands) for complete
description of handling denormalized floating-point numbers.
3.13.10.8 Optional Instructions
No optional instructions are supported.
3.14
Virtual Environment Architecture (VEA)
3.14.1
Atomic Update Primitives
Both the lwarx and stwcx instructions are implemented according to the PowerPC ISA architecture
requirements. The MPC561/MPC563 does not provide support for snooping an external bus activity
outside the chip. The provision is made to cancel the reservation inside the MPC561/MPC563 by using the
CR and KR input signals. Internal buses are snooped for RCPU accesses, and the reservation mechanism
can be used for multitask single master applications.
3.14.2
Effect of Operand Placement on Performance
The load/store unit hardware supports all of the PowerPC ISA load/store instructions. An optimal
performance is obtained for naturally aligned operands. These accesses result in optimal performance (one
bus cycle) for up to four bytes in size and good performance (two bus cycles) for double precision
floating-point operands. Unaligned operands are supported in hardware and are broken into a series of
aligned transfers. The effect of operand placement on performance is as stated in the VEA, except for the
case of 8-byte operands. In that case, since the RCPU uses a 32-bit wide data bus, the performance is good
rather than optimal.
3.14.3
Storage Control Instructions
The RCPU does not implement the following cache control instructions: icbi, dcbt, dcbi, dcbf, dcbz, dcbst,
and dcbtst .
3.14.4
Instruction Synchronize (isync) Instruction
The isync instruction causes a reflect which waits for all prior instructions to complete and then executes
the next sequential instruction. Any instruction after an isync will see all effects of prior instructions.
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...
Page 854: ...Time Processor Unit 3 MPC561 MPC563 Reference Manual Rev 1 2 19 24 Freescale Semiconductor...
Page 968: ...Development Support MPC561 MPC563 Reference Manual Rev 1 2 23 54 Freescale Semiconductor...
Page 1144: ...Internal Memory Map MPC561 MPC563 Reference Manual Rev 1 2 B 34 Freescale Semiconductor...
Page 1212: ...TPU3 ROM Functions MPC561 MPC563 Reference Manual Rev 1 2 D 60 Freescale Semiconductor...
Page 1216: ...Memory Access Timing MPC561 MPC563 Reference Manual Rev 1 2 E 4 Freescale Semiconductor...