Fnc188 - Crc / Cyclic Redundancy Check - Mitsubishi Electric MELSEC FX3U Programming Manual

FX /FX /FX Series Programmable Controllers
3G 3U 3UC
Programming Manual - Basic & Applied Instruction Edition
24.4 FNC188 – CRC / Cyclic Redundancy Check
Outline
This CRC instruction calculates the CRC (cyclic redundancy check) value which is an error check method
used in communication.
In addition to CRC value, there are other error check methods such as parity check and sum check. For
obtaining the horizontal parity value and sum check value, CCD (FNC 84) instruction is available.
CRC instruction uses "X
1. Instruction format
FNC 188
P
CRC
2. Set data
Operand Type
S
D
n
3. Applicable devices
Bit Devices
Oper-
and System User
Type
X Y M T C S D .b KnX KnY KnM KnS T C D R U \G
S
D
n
: Make sure to specify four digits (K4
Explanation of function and operation
1. 16-bit operation
CRC value is generated for "n" 8-bit data (unit: byte) starting from a device specified in
.
D
The 8-bit conversion mode and 16-bit conversion mode are available in this instruction, and the mode can be
switched by turning ON or OFF M8161. For the operation in each mode, refer to the following pages.
16 15 2
"X + X + X + 1" is used as a polynomial for generating the CRC value (CRC-16).
Command
input
FNC188
CRC
16 15 2
+ X + X + 1" as a polynomial for generating the CRC value (CRC-16).
Mnemonic
16-bit Instruction
CRC
7 steps
CRCP
Head device number storing data for which the CRC value is generated
Device number storing the generated CRC value
Number of 8-bit (1-byte) data for which the CRC value is generated or the device
number storing the number of data
Digit Specification
S
D n
24.4 FNC188 – CRC / Cyclic Redundancy Check
→ For CCD instruction (check code), refer to Section 16.5.
Operation Condition
32-bit Instruction
Continuous
Operation
Pulse (Single)
Operation
Description
Word Devices
Special
System User Index
Unit
V Z Modify K H
) when specifying the digits of a bit device.
24 Others – FNC181 to FNC189
Mnemonic Operation Condition
⎯
⎯
Data Type
16-bit binary
Others
Con- Real Charac-
Pointer
stant Number ter String
E " " P
, and stored to
S
621
21
22
23
24
25
26
27
28
29
30