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 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 own special printers, e.g. GA-46 serial printer. 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:

  1. Components necessary to prepare the formulas
  2. Start time of weighing the components
  3. Weighed components
  4. End of weighing the components

Data from the printer are asynchronous. They must be synchronous to be read. For synchronization, there are used two I/O tags with the address "TRIGGER_IN", "TRIGGER_OUT". When publishing the new data, the value of I/O tag with "TRIGGER_IN" address is incremented. When the value of I/O tag with address TRIGGER_OUT is evened up, it is the acknowledgement of reading.

At the beginning of weighing, the terminal informs about the number or 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 recording 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  

I/O tags that send the information about the start of weighing.

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 document.
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