Mitsubishi Electric MELSEC Q80BD-J71GF11-T2, User Manual

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5 FUNCTIONS
5.4 SEND/RECV Function
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Reception buffer of RECV function
Reception buffer of RECV function is a function in which a driver executes the RECV instruction automatically and received
data are stored to reception buffers of each channel number in the driver.
Set the Reception buffer of RECV function in the "driver setting" of the network parameter. (

Page 106 Driver setting)
• "Without setting"
When the reception buffer is not set, the operation is the same as the RECV function of link dedicated instruction for CPU.
This setting is used for detecting errors in sent data, whose execution type of the SEND function is set to "with arrival
confirmation", at sending side.
• "With setting"
When the reception buffer is set, the operation is the same as the RECV function for MELSECNET/H board or CC-Link IE
Controller Network board.
This setting is used for receiving data from multiple stations such as data sampling.
When the reception buffer is set, an error may occur under the following condition.

Messages received from other stations are stored to a storage channel of the target station specified in the send source.
 A driver executes the RECV instruction automatically and stores received messages to reception buffers of each channel number from the storage
channel of the target station.
A maximum of 128 reception data are stored to each reception buffer of each channel number in the driver. When received data exceeds 128, the driver
discards the received data automatically.
 Using the mdReceiveEx/mdReceive function, data of the specified channel number are read from the reception buffer in the order they were received.
Condition Description Corrective action
Data are read immediately after the
send data completion at the sending
station. When attempting data read by executing the mdReceive/mdReceiveEx
function immediately after the send data completion at the sending station,
"No reception data error" occurs because data have not yet been stored to the
reception buffer of the driver. • Retry it after a little while.
Data are sent consecutively from the
sending station. When attempting data send consecutively, "Channel busy (dedicated
instruction) error" occurs at the sending station because the channel is being
used by the driver and thus the sent data cannot be received. • Retry it after a little while.
• Change the storage channel of the
target station.
Normally completed data at the
sending side are discarded. When 128 received data are stored to the reception buffer of each channel
number, the 129th and the following received data are discarded automatically
by the driver after they are received by the board and before they are stored to
the reception buffer.
When the data, whose execution type is set to "with arrival confirmation", are
sent from the sending side, a normal completion is established at the sending
side because the board receives data once, however, data are discarded. • Retry it after a little while.
main() {
mdOpen( 181, -1, &path );
mdReceiveEx( path, 0, 255, ,
);
mdClose( path );
}
Ò
Ó
Ô
SEND
Reception buffer
of channel 1
Reception buffer
of channel 2
First data
Second data
127th data
128th data
First data
Second data
127th data
128th data
[Send source]
[Own station]
CPU module Target station Board Driver User application
Channel 1
Channel 2
Channel 1
Channel 2
RECV
instruction
RECV
function