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6. Configuring the Gateway
Configuration
element Description
Update mode This element is used to specify the transmission mode for the query on the Modbus
network. It takes one of the following four values:
- Cyclically................................. Default communication mode. The query is transmitted
periodically on the Modbus network (see “Update time”).
- On data change...................... The gateway transmits the query on the Modbus network
when at least one item of data from this query is changed by the DeviceNet master.
So this is an aperiodic communication mode.
- Single Shot .............................This transmission mode only allows a single Modbus
exchange for the whole of the time that the gateway is operating. This exchange
takes place just after the initialization of the gateway.
- Change of state on trigger...... With this aperiodic communication mode, the Modbus
query is sent every time that the DeviceNet master changes the value of an 8-bit
counter designated by the “Trigger byte address” element. For instance, this is the
case with the queries associated with “Transactions 1” and “Transactions 2”
personalized commands for the “TeSys U n°1” node of the gateway’s default
configuration. These queries are transmitted when the values of the related “trigger
bytes” (addresses 16#021E and 16#021F) are changed by the DeviceNet master.
Please see the description of this element for further information about how to use
this communication mode.
Update time
(10ms)
This element is only used by the gateway if “Update mode” is set to “Cyclically”. In this case, it
specifies the query’s transmission period on the Modbus network.
e.g. With the ATS48, we will be using the configuration shown
opposite. The most notable points of this configuration are:
• On disconnection the data is reset on one of the two networks.
• 3 re-transmissions with a 100 ms timeout.
• Periodic communications with a cycle time set to 300 ms.