M30240ECFP MITSUBISHI [Mitsubishi Electric Semiconductor], M30240ECFP Datasheet - Page 116

• Manufacturer Part Number: M30240ECFP
• Description: M30240 Group Specification
• Manufacturer: MITSUBISHI [Mitsubishi Electric Semiconductor]

Specifications in this manual are tentative and subject to change
CRC Calculation Circuit
2.25 CRC Calculation Circuit
Figure 1.105:
Figure 1.106: CRC-related registers
Figure 1.105 shows the block diagram of the CRC circuit. Figure 1.106 shows the CRC-related registers.
The Cyclic Redundancy Check (CRC) calculation circuit 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 is a 16-bit code generated for a block of a given data length in multiples of 8 bits. The
CRC code is set in a CRC data register each time one byte of data is transferred to a CRC input register
after writing an initial value into the CRC data register. Generation of CRC code for one byte of data is
completed in two machine cycles.
Block diagram of CRC circuit
(b15)
CRC data register
b7
b7
CRC input register
(b8)
b0 b7
b0
CRC input register (8)
CRC calculation result output register
Data input register
Data bus high-order bits
Data bus low-order bits
CRC code generating circuit
Eight low-order bits
CRC data register (16)
x
16
b0
+ x
12
Symbol
CRCD
Function
Symbo
CRCIN
Function
+ x
(Address 03BE
1-116
5
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
+ 1
03BD
16
Address
)
Address
16
03BE
Eight high-order bits
, 03BC
16
16
(Addresses 03BD
0000
Values that
Values that
can be set
Indeterminate
00
can be set
Indeterminate
When reset
When reset
16
16
to FFFF
to FF
Mitsubishi microcomputers
16
16
M30240 Group
16
R
R
, 03BC
W
W
16
)