Xicom XTU-400K, Operation And Installation Manual

Page: 121 / 189

MNC-0500-002 7 of 36 Revision H
Amplifier Communication and Protocol, Octagon ISA CPU
Protocol
Overview
Xicom digitally controlled devices monitor their serial ports for incoming
messages and respond to messages as soon as they are verified.
Response time varies, typically ranging between 20 and 100
milliseconds. Although devices will respond to messages with invalid
parameters, they ignore messages with invalid address bytes or check
bytes.
Message Format
•
Commands, Queries, and Responses are formatted according to
Table 1 and Table 2 on page 9
•
Messages are delineated using start and stop characters, followed
by a check byte.
•
The address byte allows a master device to selectively
communicate with individual devices that are sharing a RS-485
bus.
•
Each message has a mandatory message byte, followed by a
variable number of parameters. Some messages have no
parameters, while others can have many. The variable length
parameter field is also used to hold message responses.
RS-485
Using RS-485, a master device can maintain status and control of
multiple devices, which share send/receive lines. Slaves may transmit
only in response to a command or query from the master. Each device is
assigned a unique address between 'A' and 'Z' to differentiate it from other
devices.
RS-485 device addresses are selected on rack HPAs using the front
panel interface. They are selected on digital outdoor HPAs using Xicom's
"wRemote" utility.
Note
If a device is not responding to your messages, check the
RS-485 device address.