ProSoft Technology PS-QS-1x10-0781 - Manual (Page 55)

FieldServer Configuration Manual Page 55 of 90
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9 TIMING PARAMETERS
Under normal operation, the FieldServer will send a poll request to a Server device and that device will reply with a
response. The amount of time between successive poll requests is called the Scan_Interval. The time between
receiving a response from a Server device and the next poll request is called the Poll_Delay.
If the FieldServer sends a poll request, and the Server device does not send a response, it is considered a timeout.
The time the FieldServer waits before declaring a timeout can be adjusted by the Timeout parameter. If a timeout
occurs, then the FieldServer will retry the poll request (number of times retried is specified by the retries
parameter). The interval between Retries is specified by the Retry_Interval. The FieldServer will send poll
requests at the end of each Retry_Interval. Once the specified numbers of Retries have been sent, the FieldServer
will mark the Node offline. Once a Node has been marked offline, it will wait for a period specified by
Recovery_Interval before sending another poll request.
Once the communications have been re-established, the FieldServer will wait for a period called Probation_Delay,
before marking the Node as online.
Note 1: The Ic_Timeout parameter monitors the time between characters in a response. If the time exceeds the
Ic_Timeout, the response is discarded and is considered a Timeout.
Note 2: All parameters in bold above are configurable. See table below for where they are configured, and what
the defaults will be if they are not configured. Refer also to Appendix B.2.
Parameter Default Value Where Used
Scan_Interval 2 seconds Map Descriptor, Node, Connection
Poll_Delay 0.05 seconds Connection
Timeout 2 seconds Map Descriptor, Node, Connection
Retry_Interval 10 seconds Node
Retries 3 times Node
Recovery_Interval 30 seconds Node
Probation_Delay 1 minute Node
Ic_Timeout 0.5 seconds Map Descriptor, Node, Connection
Note 4: In the case of parameters that may be declared at the Connection, Node or Map Descriptor level, when the
parameter is declared at more than one level, the Map Descriptor declaration takes highest priority, followed by
the Node declaration and then the Connection declaration.
Note 5: A non-response from the remote Server device causes a Timeout. The driver does nothing until a response
is received or the timeout period has expired. Thus if a connection has two Nodes and one Node is producing
Timeouts this will have the effect of slowing down communication for the other Node in the sense that the driver
does nothing while the timeout timer is counting up to its setpoint. Once there is a timeout on one Node, the
driver will not retry any Map Descriptors on that Node until the Retry_Interval has expired. Thus during the
Retry_Interval the other Node will get 100% of the service.