Comtech EF Data CLC-10 - Manual (Page 38)

CLC-10 Comtech LPOD Controller Handheld Terminal M&C Accessory Revision 3
Serial-Based M&C using the CLC-10 MN-CLC10
3–6
3.4.2 EIA-232
This is a much simpler configuration in which the Controller device is connected directly to the Target via a two-wire-plus-ground
connection. Controller-to-Target data is carried, via EIA-232 electrical levels, on one conductor, and Target-to-Controller data is carried
in the other direction on the other conductor.
3.4.3 Basic Protocol
Whether in EIA-232 or EIA-485 mode, all data is transmitted as asynchronous serial characters, suitable for transmission and reception
by a UART. The character format should be 8N1 (8 data bits, no parity, 1 stop bit). In general, the baud rate may vary between 2400 and
38400 baud.
For proper communication with the CLC-10, the SSPA baud rate should be set to 9600 bps (see the SBR command /
query for configuration details).
All data is transmitted in framed packets. The Controller is assumed to be a PC or ASCII dumb terminal that is in charge of the process of
monitor and control. The Controller is the only device that is permitted to initiate, at will, the transmission of data. Targets are only
permitted to transmit when they have been specifically instructed to do so by the Controller.
All bytes within a packet are printable ASCII characters, less than ASCII code 127. In this context, the Carriage Return and Line Feed
characters are considered printable.
All messages from Controller-to-Target require a response – with one exception. This will be either to return data that has been
requested by the Controller, or to acknowledge reception of an instruction to change the configuration of the Target. The exception to
this is when the Controller broadcasts a message (such as Set time/date) using Address 0, when the Target is set to EIA-485 mode.