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6. Configuring the Gateway
6.11.2.2. Configuring the Query
Select the “Query” element from the Modbus command. The
various elements of the configuration of the query for this command
are shown opposite. The values displayed correspond to the
default values for any new command.
These elements allow you to configure how the whole command is
managed, including how degraded modes are managed (number of
re-transmissions, for example).
Each of these elements is described, in order, in the table below. When a unit is assigned to an element, it is
shown in brackets after the name of the element.
Configuration
element
Description
Minimum time
between
broadcasts
(10ms)
This element is only relevant if you have added a “Broadcaster” node (see chapter 6.13
Adding a Broadcaster Node, page 85). This parameter then allows you to specify a waiting
time following the transmission of the selected broadcast command. The next Modbus
message, whatever it is, will only be transmitted by the gateway once this time has elapsed.
So it needs to be long enough to allow the slowest Modbus slave to process the command
which has been broadcast. This parameter is not used by commands which do not belong
to a broadcaster node.
With the LUFP7 gateway’s default configuration, this feature has not been used, so as to
control the Modbus slaves individually.
Offline options
for fieldbus
This element affects the data sent to the Modbus slave, but only in the query to which this
element belongs to, whenever the gateway is disconnected from the Profibus-DP network.
This element takes one of the following three values:
- Clear ..............From now on all data sent to the Modbus slave using this query is set to
16#0000 (resetting of the output data in the gateway’s memory).
- Freeze ...........All data sent to the Modbus slave using this query retains its current values
(the output data in the gateway’s memory is frozen).
- NoScanning...The query is no more transmitted to the Modbus slave by the gateway
Offline options
for sub-network
This element affects the data sent to the Profibus-DP master PLC whenever the query to
which this element belongs to has not been answered with a response by the Modbus slave
(no response). This element takes one of the following two values:
- Clear..............From now on the data sent to the Profibus-DP master PLC is set to
16#0000 (resetting of the input data in the gateway’s memory).
- Freeze ...........From now on the data sent to the Profibus-DP master PLC retains its current
values (the input data in the gateway’s memory is frozen).
N.B. exception responses issued by the Modbus slaves do not trigger the use of these “Offline options!”
Reconnect time
(10ms)
If there is no response from the Modbus slave to a query, or following the receipt of an
incorrect response, the gateway uses the “Retries” and “Timeout time (10ms)” elements to
carry out re-transmissions. If the Modbus slave has still not responded correctly following
these re-transmissions, the gateway stop sending it the corresponding query for a period of
time which can be adjusted using “Reconnect time (10ms)”.
When this period is over, the gateway attempts to restore communication with the Modbus
slave.