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RE:4202-MNET-ASCII4
In the MNET Client Commands for the ProLinx 4202-MNET-ASCII4 module, the Slave ID parameter in the commands applies, mainly, to what is called, "Encapsulated Modbus" protocol. This is essentially Modbus Serial RTU protocol, wrapped in an Ethernet packet and transmitted to Service Port 2000 of a Modbus TCP/IP device; which then strips off the Ethernet wrapper and retransmits the serial portion of the message to the Slave ID node number in the packet.
Normal Modbus TCP/IP messages, also referred to as MBAP messages, sent to Service Port 502 on the target server, generally do not use this parameter and it is ignored.
To send ASCII messages out a particular port, you first set the TX DB Start parameter in the module configuration file for that port to some address not already in use, allowing at least 200 registers between data areas. Then, the Modbus TCP/IP Cient Read Command can use this address as the DB address to store the ASCII string codes for an outging message. You may refer to the ASCII Protocol User Manual, Section 2.1.2 to see the word offsets used for various data values of the transmit buffer area which starts at the TX DB Start address for a given port.
The basic idea is to load the TX DB area with the information needed and everytime a new string is to be transmitted, you will change the data stored in these registers and increment the Transaction Sequence Number, the first word in the data area, to trigger the output to the port. Everytime the module detects a new sequence number (and they don't really have to go in sequence, they just have to be different) it will transmit the number of characters from the data buffer, as described in Section 2.1.2 of the manual.
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