M30622MA-XXXFP RENESAS [Renesas Technology Corp], M30622MA-XXXFP Datasheet - Page 440

• Manufacturer Part Number: M30622MA-XXXFP
• Description: 16-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY
• Manufacturer: RENESAS [Renesas Technology Corp]

CRC Calculation Circuit
Operation (1) The CRC calculation circuit sets an initial value in the CRC data register.
Figure 2.10.3. Calculation example using the CRC calculation circuit
2.10.2 Operation of CRC Calculation Circuit
The following describes the operation of the CRC calculation. Figure 2.10.3 shows an example of calcu-
lation data 0123
(2) Setting 01
(3) Setting 23
(1) Setting 0000
(2) Writing 1 byte data to the CRC input register generates CRC code based on the data register.
(3) The CRC calculation circuit detects an error by means of comparing the CRC-checking data
(4) The content of CRC data register after all data is written becomes CRC code.
The code resulting from sending 01
(X
conformity with the modulo-2 operation.
Thus the CRC code becomes (1001 0001 1000 1000). Since the operation is in LSB first mode, the (1001 0001 1000 1000)
corresponds to 1189
circuit built in the M16C, switch between the LSB side and the MSB side of the input-holding bits, and carry out the CRC
operation. Also switch between the MSB and LSB of the result as stored in CRC data.
16
CRC code generation for 1 byte data finishes in two machine cycles.
with the content of the CRC data register, after the next data is written to the CRC input
register.
+ X
16
16
1 0001 0000 0010 0001 1000 0000 0000 0000 0000 0000
16
12
16
+ X
using the CRC calculation circuit.
5
+ 1), becomes the remainder resulting from dividing (1000 0000) X
b15
b15
b15
16
in hexadecimal notation. If the CRC operation in MSB first mode is necessary in the CRC operation
LSB
9
1000 1000 0001 0000 1
1189
0A41
16
8
LSB
b7
b7
in LSB first mode is (1000 0000). Thus the CRC code in the generating polynomial,
16
1000 0001 0000 1000 0
1000 1000 0001 0000 1
16
1001 0001 1000 1000
1
1
b0
b0
b0
b0
b0
1000 1000
2 cycles
After CRC calculation is complete
CRC data register
Stores CRC code
After CRC calculation is complete
CRC data register
Stores CRC code
CRC data register CRCD
CRC input register
CRC input register
MSB
MSB
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
16
[03BD
CRCD
[03BD
CRCIN
[03BE
CRCIN
[03BE
CRCD
[03BD
by (1 0001 0000 0010 0001) in
16
16
16
16
16
Modulo-2 operation is
operation that complies
with the law given below.
, 03BC
]
, 03BC
]
, 03BC
16
16
16
0 + 0 = 0
0 + 1 = 1
1 + 0 = 1
1 + 1 = 0
]
]
]
-1 = 1
Mitsubishi microcomputers
M16C / 62 Group
425