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Softing Linking Device –
Manual for Configuration, Installation and Maintenance
Appendix A - Bus Parameter Configuration
page 76 of 85 V1.3
7 Appendix A - Bus Parameter Configuration
This section will help you configure the bus parameters of an H1 device or H1 link of a
linking device correctly. It gives hints and ranges for the individual parameters.
7.1 Bus parameters relevant for H1 devices
Parameter
Description
Range/
Restriction
Default value
T1
This is the preset value for the SM service timeout timer
in 1/32 of a millisecond ticks. It defines the time which
the SM kernel of the host will wait for a response to an
SM request to the field device. If the timer expires the
service will be aborted with a negative response. Its
purpose is to ensure that devices responding to system
management requests have sufficient time to carry out
necessary actions and transmit a response. For a
description of the relationship between the three timers
refer to T3.
-
480000 (15s)
T2
This is the preset value for the SM set address
sequence timer in 1/32 of a millisecond ticks. The timer
T2 is a sequence duration timer. Its purpose is to
guarantee that incorrectly executed or incomplete
sequences are aborted in the System Management
Kernel of the device. For a description of the
relationship between the three timers refer to T3.
T2 >= T3 +
3*T1 (host)
2880000 (90s)
T3
This is the preset value for the set address wait timer in
1/32 of a millisecond ticks. This time is used by the SM
kernel of the host after a new address was assigned to
a field device to wait before checking for the field device
at the new node address. The relationship between the
three timers T1, T2 and T3 is important for the host and
the device to set the address of a field device correctly.
T1 and T3 will be used on the host side, T2 within the
field device. If the value for T2 is too small a new
address cannot be assigned to the field device because
the timeout is too small. T2 should always be >= T3 +
3*T1 of the host.
-
1440000 (45s)
SlotTime
V(ST)
Device capability for how fast the device can reply upon
receipt of a PDU. This capability is measured in
MaxResponseDelay SlotTimes, V(MRD) × V(ST). Both
parameters are specified in octet durations. The
attributes SlotTime and MaxResponseDelay should be
set such that the device represents the maximum
response delay in octets of the device. The capability
can be obtained from the devices CFF file. When
configuring an H1 Link the maximum value of the
product SlotTime × MaxResponseDelay of all devices
residing on that link should be the minimum value for
the Link configuration. This is to assure that all devices
participate on the bus.
1 - 4095
8. Support for a
value less than
the default is
recommended.
MaxRespon
seDelay
Device capability for how fast the device can reply upon
receipt of a PDU. This capability is measured in
1 - 11
10. Support for
a value less