Russound CAS44 Manual page 7

4 RNET™ Message Packet Format
0xF0 Target Device ID
Every RNET™ message has a consistent format. There are three major components; the
Message Header, Message Body and Message Trailer. Each of these is explained here in some
detail.
There are several special characters used in this protocol. The MSB (Most Significant Bit – far
left bit of an 8-bit byte – e.g., 0b
packet are low (0), except for these special characters. These special characters are the "Start of
Message Character", the "End of Message Character", and the "Invert Character", which
are explained within this document.
4.1 Message Header
Each message consists of a "Message Header" which is compiled of a Start of Message
Character, Target Device ID, Source Device ID, and the Message Type.
4.1.1 Start of Message Character
0xF0 is the special HEX value that indicates the beginning of a new message.
4.1.2 Target Device ID
The Target Device ID defines to which device we are sending the message. Every device on an
RNET™ system has a unique "Device ID" that allows messages to be sent to it. Each Device ID
consists of a Controller ID, a Zone (Port) ID and a Keypad ID. In the case of a Controller with
zone keypads, the purpose of each Device ID field is apparent.
4.1.2.1 Target Controller ID
On power up, the Controller assigns its Controller ID and a Zone ID to all keypads connected to
it. The Controller ID is set in the Controllers "Setup Menu" using 1 based numbering but in the
Device ID it is Zero-based (0x00 = 1, 0x01 = 2, 0x02 = 3, etc...). All systems have a controller
0x00 (the Root Controller) with additional controllers added (and numbered) as needed. A value
of 0x7F can be used to send messages to all devices in the system.
The Russound RNET™ system provides support for up to 6 connected controllers for a
maximum of 36 separate zones. When a multi-controller system is configured, each controller is
given a unique controller ID through the programming procedure. All of the controllers are
linked together onto a common RNET™ bus, so any messages sent to the RS232 port of
controller 1 will be available to all controllers and all keypads in the system.
Header
Source Device ID
0
0010001) of all bytes within the message body of an RNET™
Body
Type Body Checksum
Trailer
0xF7
7