Rain Bird Gold LINK 900, Руководство пользователя

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22
September 2015
5. Operation
The following provides a brief overview of the operation of the proprietary LINK communication protocol:
Communication protocol:
1. All LINK communication is a two-way polled Master/Slave type
a. The MIM-LINK / TWI-LINK is the Master
b. Satellite Controllers are Slaves
2. All communications are initiated by the central Interface
a. Field devices respond only to their unique address and only if the message type requires a
response
3. No communication is initiated by the field devices
a. A “Power Up” message output is the ONLY exception
4. Messages requiring a response are retransmitted by the Central up to 5 times
a. When a valid response is received, no further retries are attempted
5. No retries are sent for messages not requiring a response
6. Messages received in error are treated as having never been received
7. When irrigation is not occurring, the central polls a certain number of channels every two minutes
8. FCC upgrade changes made in 3rd/4th quarter of 1997
a. Central must listen for traffic before it transmits
b. Controller does not listen before it transmits
c. Controller polls reduced to 8 channels per 2 minute period when inactive
Message Types:
Different types of messages are sent by the central to the controllers in the field. Examples are:
1. Channel Station Output Request: Commands to turn on or turn off stations in the field
a. Sent every minute. Ex.: Controller #4, turn on station 6
2. Channel Poll: Status request for controllers in the field
a. All active channels are polled every 2 minutes
b. 8 inactive channels are polled every 2 minutes
3. Sensor Poll: When equipped, sensors are polled:
a. With the same timing same as channel poll
b. Controllers (COM only) with sensors respond with either current sensor ON/OFF condition or
pulse count
Message Structure:
The MIM or TWI operates on a framework of Groups and Channels. A Group is composed of 28 channels.
The MIM-LINK and the TWI-LINK are each capable of operating four groups (please note that some
central control software have a limited number of Groups available). A channel controls up to 24 Stations
on a Satellite Controller. Here are examples how channels are used:
•
Controllers having up to 24 Stations: One channel is required. If the controller has only 16
stations, it still requires the entire channel. The eight stations remaining within the structure of
that channel will not be used. They do not carry over into another channel.
•
Controllers having up to 48 stations: Two channels are required. If the Satellite Controller has
more than 24 stations, a second channel must be used by the controller. The channel number
should be the next highest channel.
•
Controllers having more than 48 stations: A third channel is required.
•
On a LINK system, it is recommended to assign channels without any gaps in the numbering