CONTREX ML-TRIM - Manual (Page 86)

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Communications Software Design
The ML–Trim Serial Communications Interface uses a polling technique to establish a
link with the host computer. With the exception of Keypad Lockout (CP-98), all of the
Control Parameters and Monitor Parameters that are accessible through the ML–Trim's
front panel keypad are also accessible through the Serial Communications Interface.
The host computer sends a twelve character record to the ML–Trim to establish the link
and the ML–Trim responds with either a conformation or an error message. Once the
ML–Trim responds, the host computer can send additional transmissions.
All of the ML–Trim's messages use the USA Standard Code for Information Interchange
(ASCII). The host computer sends three types of messages;
Parameter Send - To change CPs.
Control Command Send - To control operating states.
Data Inquiry - To monitor CPs and MPs.
These three message types, their character level descriptions in binary and ASCII, as
well as the ML–Trim's response record, are outlined in the sections that follow.