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BAT32G1x9 user manual | Chapter 32 Security features
1115 / 1149
Rev.1.02
32.3.2
CRC operation function (universal CRC).
In order to ensure safety during operation, the IEC61508 standard requires that the data need to be
confirmed even during CPU operation.
This universal CRC can perform CRC operations as a peripheral function during CPU operation. The
universal CRC is not limited to the code flash area and can be used for multi-purpose inspection. Specify the data
to be confirmed by software (user program). The CRC operation function in sleep mode can only be used during
DMA transfer.
The CRC operation function can be used in either the main system clock operation mode or the
secondary system clock operation mode.
The CRC-generated polynomial uses CRC-16-CCITT's "X
16
+X
12
+X
5
+1". Because the communication is
carried out with LSB priority, the calculation is performed after the bit order of the input data is reversed. For example,
if the data "12345678H" is sent from LSB, it is as follows as "78H", "56H", "34H", etc The order of "12H" is written to
the CRCN register, and the value of "08F6H" is obtained from the CRCRD register. This is the result of a CRC
operation on the following bit order after the bit order of the data "12345678H" is reversed.
CRCIN configure data
bit representation of data
reversed bit
representation
use polynomial to calculate
obtained result
reversed bit
representation of data
result data
CRCD data
reversed bit
representation
Note that during the execution of the program, because the modulator overrides the setting 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.
32.3.2.1
CRC Input Register (CRCIN).
This is the 8-bit register that sets the CRC calculation data for the universal CRC. The range that can be
set is "00H~FFH".
The CRCN register is set via the 8-bit memory manipulation instruction. After generating a reset signal,
the value of this register changes to "00H".
Figure 32-4
CRC Input Register (CRCIN).
Address: 400433ACH
after reset:
00HR/W
Symbol
7
6
5
4
3
2
1
0
CRCIN
bit7
~
0
function
00H
~
FFH
Data entry