MPC563XM Reference Manual, Rev. 1
Freescale Semiconductor
207
Preliminary—Subject to Change Without Notice
Several algorithms are available for prefetch control which trade off performance for power. More
aggressive prefetching increases power due to the number of wasted (discarded) prefetches, but can
increase performance by lowering average read latency.
10.2.6.8
Prefetch Triggering
Prefetch triggering can be enabled for instruction and data reads, but never by write cycles. Prefetch
triggering can be controlled for individual bus masters.
10.2.6.9
Buffer Allocation
Allocation of the line read buffers is controlled via the PFCR2 control register, specifically the line buffer
configuration (LBCFG) field described in
Section 10.2.8.3, “PFlash Configuration Register 2 (PFCR2)
.”
The LBCFG field defines the operating organization of the four line buffers. The buffers can be organized
as a pool of available resources (with all four buffers in the buffer) or with a fixed partition between buffers
allocated to instruction or data accesses. For the fixed partition, two configurations are supported. In one
configuration, buffers 0 and 1 are allocated for instruction fetches and buffers 2 and 3 for data accesses. In
the second configuration, buffers 0, 1 and 2 are allocated for instruction fetches and buffer 3 reserved for
data accesses.
10.2.6.10 Buffer Invalidation
The line read buffers can be invalidated under hardware and software control.
10.2.6.11 Wait-state Emulation
Emulation of other memory array timings are supported by the PFlash Memory Controller. This
functionality can be useful to maintain the access timing for blocks of memory which were used to overlay
Flash blocks for the purpose of system calibration or tuning during code development.
The PFlash Memory Controller will insert additional wait-states according to the upper address lines.
When these address lines are non-zero, additional cycles are added to system bus transfers. Normal system
bus termination will be extended. In addition, no line read buffer prefetches will be initiated, and buffer
hits will be ignored.
10.2.6.12 Censorship
This device includes censorship logic which affects the operation of the PFlash Memory Controller as
follows:
•
Censorship disables access to internal flash based on the censorship control word value and the
BOOTCFG[0:1] bits in the SIU_RSR.
•
Censorship logic prevents modification of the PFBAPR (PFlash BIU Access Protection Register)
bitfields associated with all masters except the core based on the censorship control word value,
the BOOTCFG[0:1] bits in the SIU_RSR, and the EXTM bit in the EBI_MCR.
The censorship control word is a 32-bit value located at the base address of the shadow row plus 0x1E0.
The flash module latches the value of the control word prior to the negation of system reset. Censorship
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