Operating instructions

A Appendix: Modbus Interface WirelessHART Fieldgate SWG70
94 Endress+Hauser
A.2 Rules for mapping
A.2.1 Automatic mapping of analog devices (HART CMD3)
Each HART device is mapped into 12 consecutive Modbus input registers. The order of HART
device mapping starting from register 13 is the same as the order of the sub-device identity summary
(returned by HART CMD84). For example, the HART device with the sub-device index=1 is
mapped starting at register 13. The device with the sub-device index = 2 is mapped starting at
register 25, and so on.
To find out the starting register reference address of a certain sub-device, use the following formula:
SMIR = 300013 + 12*(SDI-1),
whereby: "SMIR" is the starting Modbus input register of the associated HART device
"SDI" is the sub-device index value.
The following table shows an example of the mapping of the first two HART devices, i.e. the ones
associated with SDI=1 and SDI=2.
The assigned Modbus registers can be viewed in the Input Status and Input Register dialogs, see
Chapters 10.2.2 and 10.2.3
Example of Modbus
mapping of HART CMD 3
Modbus Specific Status
HART Device Status
Reference address Modbus RTU Format Sub-device index
300013 300014 AI Primary variable (loop current, mA unit) 32-bit floating point 1
300015 300016 PV Primary variable (device-specific unit)
300017 300018 SV Secondary variable (device-specific unit)
300019 300020 TV Ternary variable (device-specific unit)
300021 300022 QV Quaternary variable (device-specific unit)
300023 – ModStat Modbus Specific Status 16-bit unsigned
integer
300024 – DevStat HART Device Status
300025 300026 AI Primary variable (loop current, mA unit) 32-bit floating point 2
300027 300028 PV Primary variable (device-specific unit)
300029 300030 SV Secondary variable (device-specific unit)
300031 300032 TV Ternary variable (device-specific unit)
300033 300034 QV Quaternary variable (device-specific unit)
300035 – ModStat Modbus Specific Status 16-bit unsigned
integer
300036 – DevStat HART Device Status
Bit Parameter Description
0x01 (LSB) Cache validity Set to 1 when the HART CMD 3 cache of the device is empty.
0x02 (LSB) Identification ongoing Set to 1 when the gateway is performing a device identification
procedure.
0x04 (LSB) Device off-line Set to 1 when the device is off-line
Bit Parameter Description
0x01 Primary variable out of limits PV of a device in the network is out of limits
0x02 Non-primary variable out of
limits
SV, TV, QV of a device in the network is out of limits
0x04 Loop current saturated Loop current of a device in the network above 20 mA
0x08 Loop current fixed Loop current of a device in the network is fixed to 4 mA
(multidrop mode)
0x10 More status available Device in the network has more status available flagged
0x20 Cold start Device in the network has cold start flagged
(power failure or device reset)
0x40 Configuration changed Configuration of a device in the network has changed
0x80 Device malfunction Device in the network has malfunctioned