CONTREX MLP-Drive - Manual (Page 114)

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Communications Software Design
The MLP-Drive 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 MLP-
Drive's front panel keypad are also accessible through the Serial Communications
Interface. The host computer sends a twelve character record to the MLP-Drive to
establish the link and the MLP-Drive responds with either a conformation or an error
message. Once the MLP-Drive responds, the host computer can send additional
transmissions.
All of the MLP-Drive'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 MLP-Drive's response record, are outlined in the sections that follow.