Mitsubishi Electric MELSEC iQ-RJ71C24-R2 - Page 48

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2 DATA COMMUNICATION USING PREDEFINED PROTOCOL
2.3 Packet
Check Code
Use this element when an element indicating check code data is included in a packet.
C24 automatically calculates a specified check code at timing of sending/receiving, and adds it to a send packet or detects an
error of a receive packet.
Precautions
• When "Code Type" is "ASCII Hexadecimal", an ASCII  BIN conversion error (7F20H) may occur if a string except for '0' to
'9' 'A' to 'F' 'a' to 'f' is received.
• When "Code Type" is "ASCII Decimal", an ASCII  BIN conversion error (7F20H) may occur if a string except for '0' to '9' is
received.
• Only one check code can be placed in a packet.
• Packet elements placed behind a check code cannot be included in the calculating range.
• A check code cannot be included in the calculated range.
• When a calculated check code (Sum check/Horizontal parity/16-bit CRC) does not match a received check code, a sum
check error (7F24H) may occur.
• One or more elements are required before a check code.
Item Description Remarks
Element Name Set a name of the element. 
Processing Method Select a calculating method.
Horizontal parity/Sum check/16-bit CRC (for MODBUS)

Code Type ASCII Hexadecimal
ASCII Decimal
HEX
• When sending: Select a format in which a calculated
check code is sent.
• When receiving: Select a format in which data are
received.
Not settable when "Processing
Method" is "16-bit CRC (for
MODBUS)"
Data Length Select the data length on the line (byte).
The range is 1 to 4.
Not settable when "Processing
Method" is "16-bit CRC (for
MODBUS)"
Data Flow Forward Direction
(Upper byte  Lower byte)
• When sending: Sends a calculated check code, from the
upper byte.
• When receiving: Handles received data as a check code,
from the upper byte.
Not settable when "Processing
Method" is "16-bit CRC (for
MODBUS)", or when the "Data
Length" is set to "1 (byte)".
Reverse Direction
(Lower byte  Upper byte)
• When sending: Sends a calculated check code, from the
upper byte.
• When receiving: Receives data from the lower byte.
Effective when the data length is 2 to 4 (bytes).
Byte Swap
(by word)
• When sending: Sends a calculated check code by
swapping the upper byte and lower byte by word. When
receiving: Receives data by swapping the upper byte
and lower byte by word, and handles as a check code.
Effective when the data length is 4 bytes.
Complement Calculation Select the complement calculation.
No complement calculation/One's complement/Two's complement
Not settable when "Processing
Method" is "16-bit CRC (for
MODBUS)"
Calculating
Range
Start Select the starting element number of the calculating range.
The range is 1 to 32.

End Select the ending element number of the calculating range.
The range is 1 to 32.