Mitsubishi Electric MELSEC iQ-RJ71C24-R2 - Transmitting Data to Target Device; Sending Methods

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4 DATA COMMUNICATION USING BIDIRECTIONAL PROTOCOL
4.2 Transmitting Data to Target Device
4.2 Transmitting Data to Target Device
This section explains the data transmission from the CPU module to a target device.
Sending methods
The following shows the method of transmitting data to the target device through data communication using the bidirectional
protocol.
 Data such as control data and send data are stored in the device designated with the BIDOUT instruction, and then the
BIDOUT instruction is executed.
 The send data quantity and send data are written into the send area in the buffer memory.
 C24 transmits data by adding the control code ENQ to the head of the data.
• When sum check code is enabled in the transmission setting with Engineering tool, C24 adds the sum check code
calculated by internal processing to the end of the message and then transmits the message.
• When sum check code is disabled in the transmission setting with Engineering tool, sum check code is not transmitted.
 A response for the data transmission (for normal completion: ACK message; for abnormal completion: NAK message) is
received.
 Once the transmission processing of C24 is completed, the execution of the BIDOUT instruction is completed.
NAK
ACK
ENQ
C24
CH1/CH2
BIDOUT
Ò
Ó
Ô
Õ
Ö
CPU module
Buffer memory
Program
Target device
Transmitted area
Arbitrary data
Write
Data
Data portion Data length
Sum check code
(BIDOUT instruction)
(00H to FFH)
(00H to FFH)
(When normal)
Transmission
completed
(When abnormal)
Error
code
Contents Control timing
Transmission instruction
BIDOUT instruction completion device
BIDOUT instruction