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
| Parameter | Description | Default value |
|---|---|---|
Full Debug | Logging is enhanced with listings that enable fast error detection. | NO |
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:
- Components necessary to prepare the formulas
- The start time of weighing the components
- Weighed components
- 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.
| Address | Value type | Units |
|---|---|---|
| FORMULA NO. | Ci | |
| COMPONENT NO. | Ci | |
| NAME | TxtI | |
| TARG | Ai | kg |
| LIM1 | Ai | kg |
| LIM2 | Ai | kg |
| TOL | Ai | kg |
| END TIMER | Ci | S |
| VALVE | Ci | |
| OUTPUT 2 | TxtI |
After a list of components, the start of weighing follows. The I/O tags that contain this information are:
| Address | Value type | Units |
|---|---|---|
| FORMULA NO. | Ci | |
| START TIME | TiA |
I/O tags that inform about the results of weighing:
| Address | Value type | Units |
|---|---|---|
| FORMULA NO. | Ci | |
| NAME | TxtI | |
| ACTUAL V. | Ai | kg |
| TGT - ACTUAL | Ai | kg |
| TARGET | Ai | kg |
I/O tags that inform about the end of weighing:
| Address | Value type | Units |
|---|---|---|
| FORMULA NO. | Ci | |
| STOP TIME | TiA |
Document revisions
- Ver. 1.0 – October 8, 2012 – Creating of the document.
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