Read request is trigged by the Polling cycle. Optionaly it can be triggered by event, i.e. a
variable of type BOOL.
Write request is triggered by change of parameter value. Optionaly it can be triggererd by
event, i.e. a variable of type BOOL.
Following parameters can be set:
− Name – device name in the configuration tree
− Address – device address in a Modbus network.
− Polling cycle – time between requests (0…65535 ms)
− Timeout – maximum time to wait for reply (0…65535 ms)
− Retries – number of request retries if no reply (0…255)
− Status – status of slave device (BOOL variable)
− Polling – enable / disable polling (BOOL variable)
− Time between frames – the time span the master waits between the last response
(or timeout) and the next request (Fig. 4.5).
When constructing a Modbus network with the PR200 as a master it is necessary to observe
the following rules to speed up the process of receiving data from all devices:
− If one or more Slave are not connected or not accessible, it is recommended to
block the polling of these devices in the application using the parameter Polling' or to
minimize the parameter 'Timeout' for these devices. Otherwise, the response time
will significantly increase with the number of unavailable devices and the sum of
time-outs.
− When setting the parameter ‘Time between frames’ the number of Slaves and the
total number of requests must be taken into account. This parameter will be ignored
if the total polling time takes longer than the set value.
Fig. 4.5 Master configuration in master mode
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