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Data Sheet / User Manual RB-TW-2400
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5.4.2 Application Message Exchange
This command is used to exchange application data with the RC. It is structured as follows:
7
6
5
4
3
2
1
0
Command Byte
1 = ACK, 0 = NACK
0101: GET Message, 1101: SET Message
Length Hi
x
x
x
x
x
x
x
x
Length Lo
x
x
x
x
x
x
x
x
Application Port
x
x
x
x
x
x
x
x
Destination/Source Node ID x x x x x x x x
In the command byte it is distinguished between a write-request, thus the user wants to send a message
to the radio network, and a read-response. The read-response is initiated by the RC itself in order to
eliminate the need to poll for new messages. The read-response resembles the command “Get
Message’ and has the ACK bit set.
Length high and low fields are used to communicate the length of the application message exchanged.
The application port field is used to run several applications in parallel. Ports 0-6 can be used by the
user’s application. Port 7 is reserved for internal purposes.
The destination or source node id field is used depending on the direction of the message (from radio
network to user or from user to radio network). In case the user wants to send a message to the radio
network it is used as the destination ID. A broadcast can be sent when ‘255’ is used as destination ID.
In case the RC received a message from the radio network, the field will hold the source node if of the
original sender of the message.
If the RC internal buffer is full or it is unable to send the message, a further request to send a message
will result in a negative response, thus the ACK-bit is not set.