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MPC563XM Reference Manual, Rev. 1
956
Freescale Semiconductor
Preliminary—Subject to Change Without Notice
ETPUMCR is written to 1) eTPU itself will start this procedure
1
reading the SCM whenever allowed by
microengine. At the end of the cycle, when all the array has been read and the SCM signature is calculated,
the Host CPU can be notified via Global Exception if the MISC Accumulator does not match the value in
ETPUMISCCMPR.
The average time taken by MISC to complete the signature of the whole SCM can be given by the formula:
Average MISC period = S / (4 * f * (1 - L))
where f is clock frequency, S is SCM size in bytes and L is eTPU load (as a percentage of execution clocks
over a period of time, including TST clocks).
Further detail on MISC calculation can be found on
Section 23.4.10.3.1, “SCM Test - Multiple Input
.” The application note
AN2192 - Detecting Errors in the Dual Port RAM
(DPTRAM) Module
is also a good source of information (although it refers to TPU) on MISC signature.
1.
eTPU MISC hardware is optimized to read 32-bit words from memory and to calculate this CRC in parallel, rather than
shifting one bit at a time. The actual implementation inside eTPU, although bringing to the same results, does not match
exactly the algorithm shown here.