Crc Calculation - Renesas M16C/60 Series Hardware Manual

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M16C/6N5 Group

CRC Calculation

The Cyclic Redundancy Check (CRC) operation detects an error in data blocks. The microcomputer uses a
generator polynomial of CRC-CCITT (X
The CRC code consists of 16 bits which are generated for each data block in given length, separated in 8-bit
unit. After the initial value is set in the CRCD register, the CRC code is set in that register each time one
byte of data is written to the CRCIN register. CRC code generation for one-byte data is finished in two
cycles.
Figure 1.18.1 shows the block diagram of the CRC circuit. Figure 1.18.2 shows the CRC-related registers.
Figure 1.18.3 shows the calculation example using the CRC operation.
Figure 1.18.1 CRC Circuit Block Diagram
CRC data register
(b15)
b7
CRC input register
b7
Figure 1.18.2 CRCD Register and CRCIN Register
Rev.1.00 2003.05.30 page 200
16
+ X
Data bus high-order
Data bus low-order
CRC code generating circuit
CRCIN register
(b8)
b0 b7 b0
When data is written to the CRCIN register after setting
the initial value in the CRCD register, the CRC code can
be read out from the CRCD register.
b0
Data input
12 5
+ X + 1) to generate CRC code.
Low-order 8 bits
CRCD register
16 12 5
x +x +x +1
Symbol Address
CRCD 03BD -03BC
16
Function
Symbol Address
CRCIN 03BE
16
Function
CRC Calculation
High-order 8 bits
After reset
Indeterminate
16
Setting range
0000 to FFFF
16 16
After reset
Indeterminate
Setting range
00 to FF
16 16
RW
RW
RW
RW