Process Data
Original instructions
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Mapping I/O Data to the HART Multiplexer Scan
Use the Process Data dialog to:
Place a check mark in the I/O column next to each item you want to include in the HART multiplexer scan. Remove a check mark to remove that item from the scan. To help select or de-select items, you can click:
NOTE: When you select an item in the Process Data dialog, you also add a corresponding Device DDT variable to the Data Editor in Control Expert.
I/O Data Items
These input items can be included in the HART multiplexer scan:
Input Data Item
Data Type
Mapped by Default?
Is Default Mapping Editable?
Bytes
Module Status
Word
Yes
No
4
Channel Status: 0...(N-1)
DWord
Yes
No
8 (BMEAHI0812) 4 (BMEAHO0412)
Channel 0...(N-1) Input Data:
Instrument Status
32 bit unsigned
No
Yes
4
Primary Variable
Float
Yes
No
4
Secondary Variable
Float
Yes
Yes
4
Tertiary Variable
Float
Yes
Yes
4
Quaternary Variable
Float
Yes
Yes
4
Current Value
Float
No
Yes
4
Percent Value
Float
No
Yes
4
Update Counter
32 bit unsigned
No
Yes
4
These output items can be included in the HART multiplexer scan:
Output Data Item1
Data Type
Mapped by Default?
Is Default Mapping Editable?
Bytes
CH-ResetChanged
Byte
Yes
No
–
CH-Enable
Byte
No
Yes
–
1. When an output data item in the Process Data dialog is:
  • Selected: the item is added to the list of Device Derived Data Types (DDDT) in the Parameter Configuration dialog, where program logic dynamically controls the item value during run-time.
  • De-selected: the item is removed from the DDDT list. Program logic does not control the item value during run-time. The user can assign a static value to the item which is applied at start-up.
Module Status
The Module Status word presents a snapshot of the overall health of the HART analog I/O module and its channels.
Bit Number
Name
Description
0
Global Status
= 1 if the HART multiplexer has detected one or more of the following conditions:
  • one or more HART channels are disconnected (bit 1 (Disconnected) = 1)
  • a HART channel is connected to a field device that is materially different from the device configured for that channel; for example, a device of different device type or made by a different manufacturer. (bit 3 (Instrument Changed, Major) = 1)
  • an internal communication event—ICE—has occurred (bit 4 (ICE) = 1)
1
Disconnected
= 1 if any channel is in the disconnected (CH-Disconnected) state
2
Instrument Changed, Minor
=1 if any channel is in the instrument changed, minor (CH-MinorDiff) state
3
Instrument Changed, Major
=1 if any channel is in the instrument changed, major (CH-MajorDiff) state
4...6
—
= 0 (not used)
7
ICE
= 1 on the occurrence of an internal communication event
8...15
—
= 0 (not used)
Channel Status
The Channel Status words report the status of each of the module channels. Channel Status values are as follows:
Value
Name
Description
0
CH-Disabled
The channel is disabled.
1
CH-Connecting
The module is searching for, and attempting to connect with, a HART instrument on the channel.
2
CH-Connected
The channel is connected to a HART instrument.
3
CH-MinorDiff
One or more minor differences exist between the connected HART instrument and the instrument description in the multiplexer island configuration.
4
CH-MajorDiff
One or more major differences exist between the connected HART instrument and the instrument description in the multiplexer island configuration.
5
CH-Disconnected
This state indicates either:
  • The module discovered no HART instrument on the channel after performing 2 scans of the specified address range.
  • The module discovered a HART instrument on the channel, but the connection was lost.
The module continues to search for a HART instrument on this channel.
6...31
—
(not used)
Channel 0...(N-1) HART Instrument Specific Data Items
The module can also receive from a HART instrument, and add to the multiplexer scan, the following data items for each HART channel
Data Item
Description
Primary Variable (PV)
Manufacturer defined
Instrument Status
Reports one of the following conditions:
Value hex (bit)
Condition Description
0x80 (bit 7)
Device malfunction: a detected error rendered the instrument non-operational
0x40 (bit 6)
Configuration changed: an operation occurred that changed the instrument configuration
0x20 (bit 5)
Cold start: the instrument was reset, or power was cycled off then on
0x10 (bit 4)
More status available: additional instrument information is available via HART command 48 (Read Additional Status Information)
0x08 (bit 3)
Loop current fixed: current on the HART channel is being held at a fixed value, and is not responding to process variations
0x04 (bit 2)
Loop current saturated: current on the HART channel has reached its upper or lower limit, and cannot increase or decrease further
0x02 (bit 1)
Non-primary variable out of limits: the value of an instrument variable, other than the Primary Variable (PV), has traveled beyond its operating limits
0x01 (bit 0)
Primary variable out of limits: the value of the instrument Primary Variable (PV) has traveled beyond its operating limits
Secondary Variable (SV)
Manufacturer defined
Current Value
The actual reading of loop current, from 4...20 mA
Percent Value
The actual reading of loop current, expressed as a percent of the 16 mA range
Update Counter
A counter that is incremented on each scan
Check the documentation for your specific HART instrument to determine which of the above data items it offers.
CH-ResetChanged
Use the CH-ResetChanged data item to accept a HART instrument that the module has detected to be different from the instrument that previously was connected to the same channel. In this case, the channel has a Module Status value of either Instrument Changed, Minor or Instrument Changed, Major.
When a bit in this register transitions from 0 to 1, a HART instrument on that channel is accepted as the current instrument.
The CH-ResetChanged word includes the following bits:
Bit Number
Name
Description
0
CH-0 Reset
The 0 to 1 transition clears the changed instrument flag, and accepts the detected HART instrument as the identified instrument for that channel,
1
CH-1 Reset
2
CH-2 Reset
3
CH-3 Reset
4
CH-4 Reset
5
CH-5 Reset
6
CH-6 Reset
7
CH-7 Reset
8...15
—
(not used)
NOTE: The number of available channels is determined by the specific module.
CH-Enable
The CH-Enable output item reports and controls the state—enabled or disabled—of each of the channels of the HART I/O module. Every channel is enabled by default.
The bits in the CH-Enable word:
Bit Number
Name
Description
0
CH-0 Enable
  • 0 = disabled
  • 1 = enabled (default)
1
CH1 Enable
2
CH-2 Enable
3
CH-3 Enable
4
CH-4 Enable
5
CH-5 Enable
6
CH-6 Enable
7
CH-7 Enable
4...15
—
Set to a value of 0.
NOTE: The number of available channels is determined by the specific module.
Major and Minor Differences
When the module establishes connection with a HART instrument, it checks whether the present connection is the first connection made on the channel.
If there was a previous connection, the module checks whether the connected instrument matches the previously connected instrument. It does this by comparing the instrument-defining elements in the presently connected instrument with those recorded for the previously connected instrument.
The module gathers data from the HART instrument in the same manner whether the instrument is connected, connected with major differences, or connected with minor differences.
NOTE:
  • To see which instrument-defining element has changed, you can use HART command 0 (Read Unique Identifier) to examine the definition of the presently connected HART field device.
  • To accept a connected HART field instrument that has either major differences or minor differences, set the value of the CH-ResetChanged parameter to 1 for the appropriate channel.
Major Differences
Differences in the following definitions of a HART field instrument are described as major:
Minor Differences
The following differences in the definition of a HART field instrument are described as minor: