Yokogawa DX Serial Driver
default timeout for most serial drivers is based on a baud rate of 9600 baud or better. When using a driver
at lower baud rates, increase the timeout to compensate for the increased time required to acquire data.
Attempts Before Timeout
: This property specifies how many times the driver issues a communications
request before considering the request to have failed and the device to be in error. The valid range is 1 to
10. The default is typically 3, but can vary depending on the driver's specific nature. The number of attempts
configured for an application depends largely on the communications environment. This property applies to
both connection attempts and request attempts.
Timing
Inter-Request Delay
: This property specifies how long the driver waits before sending the next request to
the target device. It overrides the normal polling frequency of tags associated with the device, as well as
one-time reads and writes. This delay can be useful when dealing with devices with slow turnaround times
and in cases where network load is a concern. Configuring a delay for a device affects communications with
all other devices on the channel. It is recommended that users separate any device that requires an inter-
request delay to a separate channel if possible. Other communications properties (such as communication
serialization) can extend this delay. The valid range is 0 to 300,000 milliseconds; however, some drivers may
limit the maximum value due to a function of their particular design. The default is 0, which indicates no
delay between requests with the target device.
Note
: Not all drivers support Inter-Request Delay. This setting does not appear if it is not available.
Device Properties — Auto-Demotion
The Auto-Demotion properties can temporarily place a device off-scan in the event that a device is not
responding. By placing a non-responsive device offline for a specific time period, the driver can continue to
optimize its communications with other devices on the same channel. After the time period has been
reached, the driver re-attempts to communicate with the non-responsive device. If the device is responsive,
the device is placed on-scan; otherwise, it restarts its off-scan time period.
Demote on Failure
: When enabled, the device is automatically taken off-scan until it is responding again.
Tip
: Determine when a device is off-scan by monitoring its demoted state using the _AutoDemoted
system tag.
Timeouts to Demote
: Specify how many successive cycles of request timeouts and retries occur before the
device is placed off-scan. The valid range is 1 to 30 successive failures. The default is 3.
Demotion Period
: Indicate how long the device should be placed off-scan when the timeouts value is
reached. During this period, no read requests are sent to the device and all data associated with the read
requests are set to bad quality. When this period expires, the driver places the device on-scan and allows for
another attempt at communications. The valid range is 100 to 3600000 milliseconds. The default is 10000
milliseconds.
Discard Requests when Demoted
: Select whether or not write requests should be attempted during the
off-scan period. Disable to always send write requests regardless of the demotion period. Enable to discard
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