Transmitting Data To Target Device; Sending Methods - Mitsubishi Electric MELSEC iQ-R Series User Manual

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.
CPU module
Program
Ò
Write
(BIDOUT instruction)
Contents
Transmission instruction
BIDOUT instruction completion device
BIDOUT instruction
 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.
4 DATA COMMUNICATION USING BIDIRECTIONAL PROTOCOL
96
4.2 Transmitting Data to Target Device
C24
Buffer memory
Transmitted area
Ó
Data
(00H to FFH)
Ö
Transmission
completed
CH1/CH2
Arbitrary data
Ô
Sum check code Data portion Data length
(00H to FFH)
Õ
ACK
Error
NAK
code
Control timing
BIDOUT
Target device
ENQ
(When normal)
(When abnormal)