There are a few important points to
keep in mind when using Flash or OTP memory:
- Reads of USER OTP locations are
hardwired for 9 wait states. The RWAIT bits have no effect on these locations.
- CPU writes to Flash or OTP memory addresses
are ignored, and complete within a single cycle. Flash memory can only be
modified by issuing program or erase commands, using the Flash API.
- When a security zone is in the
locked state, and the respective password lock bits are not all ones, then:
- Data reads to Zx-CSMPSWD
return zero;
- Program space reads to
Zx-CSMPSWD return zero; and
- Program fetches to
Zx-CSMPSWD return zero.
- When the Code Security Module (CSM)
is secured, reads to Flash or OTP memory addresses from outside the secure zone
take the same number of cycles as a normal access. However, the read operation
returns zero.
- The arbitration scheme in the Flash wrapper prioritizes CPU accesses in the fixed priority order of
data space read (highest priority), program space read, and program
fetches/program prefetches (lowest priority).
- When Flash state machine is
activated for erase or program operations, the contents of the prefetch buffer
and data cache are automatically flushed.
Note: ECC checks are performed on data
read from Flash before the data is stored in the prefetch buffer or data cache. Once
data has entered the cache or buffer, there are no further ECC checks
performed.