M306H7MG-XXXFP Datasheet, PDF (180/329 Pages) Renesas Technology Corp – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER with DATA ACQUISITION CONTROLLER

M306H7MG-XXXFP/MC-XXXFP/FGFP
13. CRC CALCULATION
13. CRC Calculation
The Cyclic Redundancy Check (CRC) operation detects an error in data blocks. The microcomputer uses a generator
polynomial of CRC_CCITT (X¹⁶ + X¹² + X⁵ + 1) to generate CRC code.
The CRC code consists of 16 bits which are generated for each data block in given length, separated in 8 bit units.
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 13.1 shows the block diagram of the CRC circuit. Figure 13.2 shows the CRC-related registers.
Figure 13.3 shows the calculation example using the CRC operation.
Data bus high-order
Data bus low-order
Eight low-order bits
CRCD register
Eight high-order bits
CRC code generating circuit
x¹⁶ + x¹² + x⁵ + 1
CRCIN register
Figure 13.1 CRC Circuit Block Diagram
CRC data register
(b15)
b7
(b8)
b0 b7
b0
Symbol
Address
After reset
CRCD
03BD16 to 03BC16 Indeterminate
Function
Setting range RW
When data is written to the CRCIN register after setting
the initial value in the CRCD register, the CRC code can
000016 to FFFF16 _RW
be read out from the CRCD register.
CRC input register
b7
b0
Symbol
CRCIN
Data input
Function
Figure 13.2 CRCD Register and CRCIN Register
Address
03BE16
After reset
Indeterminate
Setting range RW
0016 to FF16 _RW
Rev.2.10 Oct 25, 2006 Page 180 of 326
REJ03B0152-0210