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MPC563XM Reference Manual, Rev. 1
Freescale Semiconductor
281
Preliminary—Subject to Change Without Notice
The third case that can cause an error response to the AHB is when a write access is attempted to the Flash
array and is disallowed by the state of the control input. This case is similar to case 1.
A fourth case involves an attempted read access while the Flash array is busy doing a write (program) or
erase operation if the appropriate read-while-write control field is programmed for this response. The 3-bit
read-while-write control allows for immediate termination of an attempted read, or various
stall-while-write/erase operations are occurring.
The Flash BIU can also terminate the current AHB access if
hready_in
is asserted before the end of the
current bus access. While this circumstance should not occur, this does not result in an error condition
being reported, as this behavior is initiated by the AHB. In this circumstance, the Flash BIU control state
machine completes any Flash array access in progress (without signaling the AHB) before handling a new
access request.
11.7.7
Access Pipelining
The Flash controller does not support access pipelining since this capability is not supported by the
low-cost Flash array. As a result, the APC (Address Pipelining Control) field should always be the same
value as the RWSC (Read Wait State Control) field, that is, BKn_APC = BKn_RWSC.
11.7.8
Flash Error Response Operation
The Flash array may signal an error response by asserting
bkn_fl_xfr_err
to terminate a requested access
with an error. This may occur due to an uncorrectable ECC error, or because of improper sequencing
during program/erase operations. When an error response is received, the Flash BIU does not update or
validate a page read buffer. An error response may be signaled on read or write operations. For more
information on the specifics related to signaling of errors, including Flash ECC, refer to the low-cost Flash
array documentation. For additional information on the system registers which capture the faulting
address, attributes, data and ECC information, see the MCM block guide.
11.7.9
Bank0 Page Read Buffers and Prefetch Operation
The logic associated with bank0 of the Flash BIU contains four 128-bit page read buffers which are used
to hold data read from the Flash array. Each buffer operates independently, and is filled using a single array
access. The buffers are used for both prefetch and normal demand fetches.
Prefetch triggering is controllable on a per-master and access-type basis. Bus masters may be enabled or
disabled from triggering prefetches, and triggering may be further restricted based on whether a read
access is for instruction or data. A read access to the Flash BIU may trigger a prefetch to the next sequential
page of array data on the first idle cycle following the request. The access address is incremented to the
next-higher 16-byte boundary, and a Flash array prefetch is initiated if the data is not already resident in a
page buffer. Prefetched data is always loaded into the least-recently-used buffer.
Buffers may be in one of six states, listed here in prioritized order:
1. Invalid - the buffer contains no valid data
2. Used - the buffer contains valid data which has been provided to satisfy an AHB burst type read
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