Engineering
WirelessHART Fieldgate SWG70
100
E Hauser
10.5.7 Diagnostic bits in cyclic data exchange
The cyclic data contain 4 error bits for every HART device. Each of these error bits can
suddenly appear during cyclic communication either when communication is lost or the
configuration of one or more devices has changed.
.HARTCommFail
This bit indicates that the device with the HART descriptor calculated from the cyclic
connection number and the data offset cannot be reached, does not respond or is still
initializing. The bit is reset as soon as the device is initialized. This bit is reset as soon as
the connection is lost.
.DescriptorNotUnique
The HART descriptors of all the devices in the WirelessHART network are read during the
basic device identification procedure. If EtherNet/IP discovers that more than two devices
share the same HART descriptor, the ".DescriptorNotUnique" bit is flagged in the cyclic data
exchange for the devices concerned. In addition, the ".DescriptorNotUnique" bit is also
flagged in the cyclic data exchange for WirelessHART itself to indicate that at least one
HART descriptor collision has been detected.
As devices with identical HART descriptors would share the same data offset in the same
cyclic connection, the cyclic data would be populated by random data from these devices. To
avoid this, the cyclic data are populated with the data of the device for which the identical
HART descriptor was first discovered. This prevents the loss of cyclic data if a new HART
device with an identical HART descriptor is added to the network.
Footnote
number
Description
1)
Status values only apply if the associated values PV, SV, TV or FV are valid. The default value "0"
indicates that either no value has been received up to now (PV, SV, TV, or FV are invalid) or that
the associated values are really bad (PV, SV, TV, FV do not have "Quiet NaN" as a value).
Use the following status for HART 5 devices that do not support burst command CMD 9:
• 00-hex: Not connected as long as no values are received from the device (PV, SV, TV, FV
contains Quiet NaN)
• C0-hex: Connected, if the values for PV, SV, TV, FV contain valid data from the device
2)
Always valid as long as the ".HARTCommFail" bit is not flagged. All the values are invalid
whenever the ".HARTCommFail" bit is flagged.
3)
If this bit is "1", none of the other data in "Device_struct (including substructures)" are valid.
4)
Only valid for HART devices with Revision 6 and higher that support burst command 9 or 48.
5)
HART devices with Revision 5 return the content of command 12 (Read Message) in the "Long
Tag" field because the long tag is not defined in HART Revision 5. Message data also contain
32 bytes.
6)
If "Cmd48Data" is populated by 0x00, this does still not indicate that "Cmd48Data" is invalid.
"Cmd48Data" is only invalid if ".NoCmd48BurstConfigured" is also flagged.
