MT Printer communication protocol

• Protocol specification

• Communication line configuration

• Communication station configuration

• I/O tag configuration

• Set of I/O tags

• Document revisions

Protocol specification

The Mettler Toledo weighing terminals can print the results from the measurement and the information about the asynchronous activities on their own special printers, e.g. GA-46 serial printer. The MT Printer communication protocol is used for processing the information from the terminal output and publishing them in the form of I/O tags.

Communication line configuration

When setting the serial communication interface, you should realize that the interface for the printer has the fixed parameters.

• Baud rate: 9600

• Parity: even

• Flow control: XON/XOF

• Data bits: 8

• Stop bits: 1

Supported line categories for the protocol: "Serial" and "SerialOverUDP Device Redundant".

Communication station configuration

Station protocol parameters

I/O tag configuration

Allowed I/O tags: Ai, Ci, Co, Di, TxtI, TiA

Set of I/O tags

The outputs from the printer, which are necessary to analyze the weighing results can be categorized into four basic groups:

1. Components necessary to prepare the formulas

2. The start time of weighing the components

3. Weighed components

4. End of weighing the components

Data from the printer are asynchronous. To ascertain their reading, they must be processed synchronously. For synchronization, two I/O tags with addresses "TRIGGER_IN" and "TRIGGER_OUT" are used. When publishing the new data, the value of the I/O tag with the "TRIGGER_IN" address is incremented. Set the value of the I/O tag with address TRIGGER_OUT to the same value, as an acknowledgment that that data was processed.

At the beginning of weighing, the terminal informs about the formula number (a unique identifier of formula), which will be weighted. Then, the list of all necessary components is sent sequentially. I/O tags in the table below are used for receiving these data.

After a list of components, the start of weighing follows. The I/O tags that contain this information are: