User manual

Rockwell Automation Publication 1769-UM011I-EN-P - February 2013 63
Communicate over Networks Chapter 4
4. Specify DF1 Radio Modem system protocol settings.
5. Click OK.
Advantage of Using DF1 Radio Modem Protocol
The primary advantage of using DF1 radio modem protocol for radio modem
networks is in transmission efficiency. Each read/write transaction (command
and reply) requires only one transmission by the initiator (to send the command)
and one transmission by the responder (to return the reply). This minimizes the
number of times the radios need to key-up to transmit, which maximizes radio
life and minimizes radio power consumption. In contrast, DF1 half-duplex
protocol requires five transmissions for the DF1 master to complete a read/write
transaction with a DF1 slave - three by the master and two by the slave.
The DF1 radio modem driver can be used in a pseudo master/slave mode with
any radio modems, as long as the designated master node is the only node
initiating MSG instructions, and as long as only one MSG instruction is triggered
at a time.
For modern serial radio modems that support full-duplex data port buffering and
radio transmission collision avoidance, the DF1 radio modem driver can be used
to set up a masterless peer-to-peer radio network. In a peer-to-peer radio
network, any node can initiate communication to any other node at any time, as
long as all of the nodes are within radio range so that they receive each other’s
transmissions.
Setting Description
Station Address Specifies the node address of the controller on the serial network. Select a number 1… 254 decimal, inclusive.
To optimize network performance, assign node addresses in sequential order. Initiators, such as personal computers, should be assigned the
lowest address numbers to minimize the time required to initialize the network.
Error Detection Click one of the radio buttons to specify the error detection scheme used for all messages.
• BCC - the processor sends and accepts messages that end with a BCC byte.
• CRC - the processor sends and accepts messages with a 2-byte CRC.
Enable Store and Forward Check the Enable Store and Forward checkbox if you want to enable the store and forward functionality. When enabled, the destination
address of any received message is compared to the Store and Forward tag table. If there is a match, the message is then forwarded
(re-broadcasted) from the port.
From the Store and Forward Tag pull-down menu, choose an integer (INT[16]) tag.
Each bit represents a station address. If this controller reads a message destined for a station that has its bit set in this table, it forwards the
message.
Also note, the Enable Store and Forward function is usable only if the controller is connected to the master radio modem.