21-22
MPC561/MPC563 Reference Manual
MOTOROLA
UC3F Operation
NOTE
After setting/clearing UC3FCTL[HSUS], reset, programming
writes, erase interlock write, setting EHV, clearing SES or
setting/clearing SIE, the page buffers may not contain valid
information. The UC3F forces an off-page read before an
on-page read can be accomplished to ensure data coherency.
For information regarding how the two read page buffers in the UC3F EEPROM are
The UC3F module is configured as a page mode memory. The UC3F module uses an
internal address comparator to monitor incoming addresses to determine if the addressed
information is stored in a read page buffer. When the address comparator determines that
the requested information is not stored in a read page buffer, an array off-page read
operation retrieves 32 bytes of data from the Flash array and transfers the addressed data to
the data bus.
In the MPC563, the UC3F module contains two 32-byte read page buffers. In the module,
one buffer is dedicated to the most recently accessed instruction fetches and the other read
page buffer is dedicated to the most recently loaded data access.
21.3.3.1 Array On-Page Read Operation
An internal address comparator is used to determine if addressed information is stored in a
read page buffer. If the address of a read access matches data contained in a read page
buffer, that addressed data is transferred from the read page buffer to the data bus. An
off-page read access to transfer data from the Flash array to the data bus is not performed
in this case.
21.3.4
Shadow Row Select Read Operation
The normal array is accessed when the SIE register bit in the UC3FMCR = 0. When
SIE = 1, reads to the array access the shadow information row.
21.3.5
Array Program/Erase Interlock Write Operation
The only valid writes to the UC3F array are program or erase interlock writes. In the case
of program interlock writes, the address of the write determines the location to be
programmed while the data written is transferred to the program data latches to be
programmed into the array. Address and data written during an erase interlock write is a
“don’t care” and is not stored anywhere.