Mitsubishi Electric MELSEC iQ-R Series User Manual page 92

Contents of received data
The following shows the contents of data to be received, including data to be transmitted. (Page 97 Send area and send
data arrangement)
■Control codes
The types of control codes are shown in the table below.
Signal Code
name (hexadecimal)
ENQ 05H
ACK 06H
NAK 15H
• Target device  C24
C24 checks and processes the control code received.
It cannot be read from the program.
• C24  target device
C24 adds the control code to be transmitted.
■Data length
This indicates the number of bytes or words for the data portion of the message.
The unit of data length (words/bytes) is in accordance with the word/byte units designation with Engineering tool.
• Target device  C24
C24 checks the length of the data received.
When the reception is normal, C24 stores the received data in the receive data storage area in the C24 buffer memory,
assigning the first byte as the lower byte (L).
• C24  target device
The length of data to be transmitted is the send data quantity designated by the program using the BIDOUT instruction.
C24 transmits this value as is from the lower byte (L).
■Data portion
This consists of an array of original one-byte data to be transmitted to the target device side, which can handle 00H to FFH
code data.
• Target deviceC24
If the receive data portion is normal, C24 takes the codes as is and stores them in the receive data storage area in
sequence, beginning with the lowest address.
The storage size is in accordance with the data length in the message and the word/byte units designation with Engineering
tool.
• C24  target device
The portion of data to be transmitted is the send data designated by the program using the BIDOUT instruction.
C24 transmits the data for the send data quantity according to the word/byte units designation with Engineering tool from
the lowest address in the send data specification area using the code as is.
4 DATA COMMUNICATION USING BIDIRECTIONAL PROTOCOL
90
4.1 Receiving Data from Target Device
Description
Enquiry
Acknowledge
Negative Acknowledge
Application
Code for starting data transmission
Response code to the target side when data was received normally
Response code to the target side when data could not be received normally
(Error code is sent immediately after the response code.)