Beckhoff EP6002-0002, Documentation

Page: 31 / 64

Commissioning/Configuration
EP6002-0002 31 Version: 1.0
4.2.3 Communication by PLC program
Sending data
You can transmit up to 22 bytes of data to the module in one PLC cycle.
1. Write the data to be transmitted in the output variables DataOut 0 ... DataOut 21.
2. Set the Output Length parameter in the Control word [
}
14] to the number of bytes to be transmitted.
3. Toggle the Transmit Request bit in the Control word [ } 14] .
ð
The module acknowledges the data transmission in the Status word [
}
14] via the Transmit Accepted
parameter.
Receiving data
If the module toggles the Receive Request bit in the Status word [
}
14] , this means that there are new
receive data.
1. Read the Input Length parameter from the Status word [
}
14] . It contains the number of bytes to be
received.
ð
The data are provided in DataOut 0 ... DataOut 21. The first datum is contained in DataIn 0.
2. After reading the data, acknowledge this by toggling the Receive Request bit in the Control word [
}
14] .
The module only makes new data available after that.
Optimization of transfer rates
In normal operating mode the data received will be adopted immediately into the process image. In order to
enable a contiguous data stream, the "Enable transfer rate optimization" option in the Settings object is
activated by default. Due to this switch, the data will first be stored intermediately in the receive buffer
(864 bytes).
The data will only be copied into the process image if no further character is received for 16 bit times or if the
buffer is full.
Continuous transmission of data
A continuous data stream is indispensable for many applications. For this purpose, the Beckhoff modules
feature the "Enable send FIFO data continuous" setting in the Settings object. The internal transmit buffer
(128 bytes) of the box can be filled first by setting this switch. After that the entire contents of the buffer can
be transmitted without interruption. To this end, data will be sent from the controller to the box as in a normal
transmission. The data from the buffer is only sent with a rising edge of the "Send continuous" bit. If the data
has been transferred, the box informs the controller by setting the "Init accepted" bit. "Init accepted" is
cleared with "SendContinuous".
Prioritization
Since received data normally cannot be repeated from the other transmitter, they have a higher priority in the
module than data to be transmitted.
Furthermore, the priority decreases as the channel number increases. Hence, the reception of data on
channel 1 has the highest priority.