m30833fjgp Renesas Electronics Corporation., m30833fjgp Datasheet - Page 266

• Manufacturer Part Number: m30833fjgp
• Description: Renesas 16/32-bit Single-chip Microcomputer M16c Family / M32c/80 Series
• Manufacturer: Renesas Electronics Corporation.

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19. CRC Calculation
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Figure 19.1 CRC Calculation Block Diagram
Figure 19.2 CRCD Register and CRCIN Register
2
0
The CRC (Cyclic Redundancy Check) calculation detects an error in data blocks. A generator polynomial
of CRC_CCITT (X
The CRC code is a 16-bit code generated for a block of data of desired length. This block of data is in 8-bit
units. The CRC code is set in the CRCD register every time one-byte data is transferred to the CRCIN
register after a default value is written to the CRCD register. CRC code generation for one-byte data is
completed in two cycles.
Figure 19.1 shows a block diagram of a CRC circuit. Figure 19.2 shows registers related to CRC. Figure
19.3 shows an example of the CRC calculation.
1
C
9
3 .
B
8 /
0
1
3
0
3
J
G
4
a
0 -
n
o r
CRC Input Register
b7
CRC Data Register
b15
3 .
1
u
, 1
3
p
1
2
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M
0
0
3
6
2
b8 b7
C
16
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8 /
+ X
, 3
M
12
3
+ X
2
C
b0
f o
b0
8 /
5
4
3
After default value is written to the CRCD
register, the CRC code can be read from the
CRCD register by writing data to the CRCIN
register. Bit position of the default value is
inversed. The inversed value is read as the CRC
code.
+ 1) generates CRC code.
Data input.
Inverse bit position of data.
8
) T
8
Symbol
CRCIN
Symbol
CRCD
CRCIN register
High-order bits of data bus
Low-order bits of data bus
CRC code generation circuit
8 low-order bits
x
16
Function
Function
+ x
Address
037E
CRCD register
Address
037D
12
16
16
+ x
- 037C
5
+ 1
16
8 high-
order bits
After Reset
Indeterminate
After Reset
Indeterminate
0000
Setting Range
Setting Range
00
16
16
to FF
to FFFF
16
19. CRC Calculation
16
RW
RW
RW
RW