24.3.2 CRC operation function (general CRC)
In order to ensure safety during operation, the IEC61508 standard requires that the data need to be
confirmed even in CPU operation.
This generic CRC can be used as a peripheral function for CRC operations in CPU operation. Generic CRC
is not limited to code flash areas but can be used for multi-purpose inspections. The data to be confirmed is
specified through the software (user program). The CRC operation function in sleep mode can only be used
during DMA transmission.
CRC arithmetic functions can be used in either the main system clock operation mode or the secondary
system clock operation mode.
CRC generates polynomials using CRC-16-CCITT's X
16
+X
12
+X
5
+1. Because the communication is
considered to be carried out in LSB first, the calculation is performed after the bit order of the input data is
reversed. For example, in the case of sending data 12345678H from the LSB, follow the requirements of 78H,
56H, 34H, 34H The 12H sequence writes the value to the CRCIN register, and the value of 08F6H is
obtained from the CRCD register. This is the result of CRC operations for the following bit order after inverting
the bit order of the data 12345678H.
Note During the execution of the program, because the modulator rewrites the set line of the software breakpoint as a
breakpoint instruction, if you set the software breakpoint in the object area of the CRC operation, the CRC
operation result is different.
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