PLX51-HART-4I / PLX51-HART-4O
♦
HART Input/Output
Setup
Multidrop Field Devices
User Manual
ProSoft Technology, Inc.
Page 35 of 127
Modbus TCP/IP
The required HART command and specific Modbus Offsets will need to be entered
into the builder window as shown below.
Figure 3.22 – Custom HART Command Builder Mapping (for Modbus TCP)
Each HART channel is allowed up to 500 bytes of mapping data for custom HART
commands. The custom HART command Modbus Holding Register range for each
HART channel is shown below:
Table 3.5 – Custom HART Data Modbus Ranges
HART Channel
Modbus HR Range
0
HR 5000 – HR 5249
1
HR 5250 – HR 5499
2
HR 5500 – HR 5749
3
HR 5750 – HR 5999
Each Custom HART command requires four mapping parameters in addition to the
HART command:
Table 3.6 – Custom HART command build parameters
Modbus
Parameter
Description
Trigger Offset
The Trigger Offset parameter is the Modbus HR offset in the Modbus HR range
(for the specific HART channel) for the trigger of the HART custom message.
For example, if the trigger offset entered is 5 and the custom HART command
is on HART channel 0, then the message trigger will be at Modbus HR 5005
(HR 5000
for HART channel 0
+ offset HR 5). If the trigger offset entered is 10
and the custom HART command is on HART channel 1, then the message
trigger will be at Modbus HR 5260 (HR 5250
for HART channel 1
+ offset HR
10).
The trigger parameter is used to trigger the start of the custom HART message
execution. Each time the trigger Modbus HR is changed to a value different
from the previous value, it will send the custom HART command.
NOTE:
Changing the trigger to value 0 will not trigger the custom HART
command.
Source Data Offset The source data offset parameter is the location in the Modbus HR range
where the HART data to be sent is stored.