Function Description
The XMIT (Transmit) function block
sends Modbus messages from a master PLC to multiple slave PLCs or
sends ASCII character strings from the PLC's Modbus slave port #1
or port #2 to ASCII printers and terminals.
XMIT sends these messages through telephone dialup modems, radio modems, or direct connection.
XMIT performs general ASCII input functions in the communication mode including simple ASCII and terminated ASCII. You may import ASCII or binary data into your PLC and convert it into various ASCII or binary data to send to DCE devices (Data Communication Equipment) based upon the needs of your application.
XMIT block differs from
the XXMIT block only in the interface.
Therefore for the functional descriptions, see XXMIT.EN and ENO can be configured as additional parameters.
Diagnostics
The block has built-in diagnostics that check that no other XMIT block is active in the PLC on the same port. In the block a control table allows you to control the communication link between the PLC and the DCE devices attached to Modbus port #1 or port #2 of the PLC. The block does NOT activate the port LED when it is transmitting data.
XMIT with Multiple Modbus Masters
As a master/slave protocol, Modbus is designed to have only one master polling multiple slaves. Therefore, when using the XMIT block in a network with multiple masters, contention resolution and collision avoidance is your responsibility and may easily be addressed through user logic programming.
Restrictions
The block controls Modbus port #1 and #2 of the Momentum CPUs. It can be used with the stripped exec only. It works just as its LL984 counterpart, but without ASCII string conversion, copy and compare functions and without the Port Status functions.