RM0367 Rev 7 75/1043
RM0367 Flash program memory and data EEPROM (FLASH)
122
Data buffering
In the NVM, six buffers can impact the performance (and in some conditions help to reduce
the power consumption) during read operations, both for fetch and data. The structure of
one buffer is shown on Figure 3.
Figure 3. Structure of one internal buffer
Each buffer stores 3 different types of information: address, data and history. In a read
operation, if the address is found, the memory interface can return data without accessing
the NVM. Data in the buffer is 32 bit wide (even if the master only reads 8 or 16 bits), so that
a value can be returned whatever the size used in a previous reading. The history is used to
know if the content of a buffer is valid and to delete (with a new value) the older one.
The buffers are used to store the value received by the NVM during normal read operations,
and for speculative readings. Disabling the speculative reading makes that only the data
requested by masters is stored in buffers, if enabled (default). This can increase the
performance as no wait state is necessary if the value is already available in buffers, and
reduce the power consumption as the number of reads in memory is reduced and all
combinatorial paths from memory are stable.
The buffers are divided in groups to manage different tasks. The number of buffers in every
group can change starting from the configuration selected by the user (see Table 14). The
total number of buffers used is always 6 (if enabled). The history is always managed by
group.
The memory interface always searches if a particular address is available in all buffers
without checking the group of buffers and if the read is fetch or data.
At reset or after a write/erase operation that changes several addresses, all buffers are
empty and the history is set to EMPTY. After a program by word, half-word or byte, only the
buffer with the concerned address is cleaned.
MS32395V1
Address
Value
History
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