Comtech EF Data CLO-10 - Manual (Page 114)

CLO-10 Link Optimizer Revision 1
Remote Control MN/CLO-10.IOM
RS-485 (full duplex) summary:
Two differential pairs - one pair for Controller-to-target, one pair for Target-to-controller.
a. Controller-to-target pair has one line driver (controller), and all targets have line-
receivers.
b. Target-to-controller pair has one line receiver (controller), and all targets have tri-
state drivers.
B.3 RS-232
This 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 RS-232
electrical levels, on one conductor, and target-to-controller data is carried in the other direction on
the other conductor.
B.4 Basic Protocol
Whether in RS-232 or RS-485 mode, all data is transmitted as asynchronous serial characters,
suitable for transmission and reception by a UART. In this case, the asynchronous character
format is fixed at 8N1. The baud rate may vary between 1200 and 38,400 baud.
All data is transmitted in framed packets. The controller is assumed to be a PC, which is in charge
of the process of monitor and control. The controller is the only device, which 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, which 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 RS-485 mode.
B.5 Packet Structure
Controller-to-target:
Start of Packet
Target
Address
Address
De-limiter
Instruction
Code
Code Qualifier
Optional
Arguments
End of Packet
<
ASCII code 60
(1 character)
(4 characters)
/
ASCII code 47
(1 character)
(3 characters)
= or ?
ASCII code 61 or 63
(1 character)
(n characters)
Carriage
Return
ASCII code 13
(1 character)
Example: <0135/TRQ=70.2345{CR}
B-2