Transient Transmission; Message Communication - Mitsubishi Electric MELSEC Q Series User Manual

13.3

Transient Transmission

Transient transmission is a communication method to communicate data by using the sequence program link
dedicated instructions in the programmable controller system.
In the C Controller module, use the dedicated function library for the user program.
There are 2 methods for transient transmission: message transmission by controlled network module channel and
direct access to the other station device(s).
13.3.1

Message communication

Message communication is a method to read/write data by using controlled network module channel from the C
Controller module.
Use the dedicated function library for the user program to establish the message communication.
The message communication function allows for data communication equivalent to link dedicated instructions, SEND/
RECV instructions.
(1) Data flow
Data flow in message communication is illustrated below.
Sending side
C Controller module
User program
ret = QBF_SEND();
or
ret = mdSendEx();
1) The sending C Controller module utilizes the user program's message transmission function to specify the
host channel and destination channel(s) and then performs transmission.
2) From the sending channel, data are transmitted to the receiving channel(s).
3) The receiving C Controller module(s) (other) automatically confirms the receiving channel(s) and stores the
received data in the internal buffer for message reception.
4) The receiving C Controller module(s) (other) reads messages from the internal buffer for message reception
by using message reception functions of the user program.
● When communicating massages with CPU modules other than the C Controller module
The message communication function is also available for CPU modules with sending or receiving station(s) that is not
the C Controller module.
In destination CPU module(s), use the link dedicated instructions, SEND/RECV instructions, or equivalent functions.
● When sending data twice to the same channel of the receiving station with ACK set
Do this after the receiving station(s) reads data by using a message reception function (or a RECV instruction).
If the sending station transmits data to the same channel as the receiving station(s) before read-out completion by the
receiving station(s), an error occurs. If an error is detected, retry the transmission after a little while.
CHAPTER 13 FUNCTIONS ACCESSED VIA A NETWORK MODULE
Network Network
module module
Channel 1
Channel 1
1)
Channel 2 Channel 2
Channel 3
Channel 3
2)
Channel 4
Channel 4
Channel 5
Channel 5
Channel 6
Channel 6
Channel 7
Channel 7
Channel 8
Channel 8
Network No.1
Q24DHC-LS
Q24DHC-V Q24DHC-VG
Q24DHC-LS
Q24DHC-V Q24DHC-VG
Receiving side
C Controller module (other station)
User program
Internal buffer for
ret = QBF_RECV();
message reception
4)
or
1st
ret = mdReceiveEx();
2nd
3)
127th
128th
Q26DHC-LS
Q12DC-V
13
Q26DHC-LS
Q12DC-V
221