ProSoft Technology MVI69-HART - Manual (Page 95)

MVI69-HART ♦ CompactLogix Platform Reference
HART Multi-drop Master Communication Module User Manual
ProSoft Technology, Inc. Page 95 of 169
March 29, 2012
Auto-Poll Modes
Each HART channel can be set to operate in three different modes:
Point-to-Point
Multi-drop
User Mode
Using the configuration file, choose the auto-poll mode through the Auto-Poll
Code parameter (P, M, or N). In the first two modes, the module will
automatically collect data from each HART instrument on the channel (auto-poll)
and store the data in the module's database.
In User Mode, the module will only execute the commands in the user command
list and will not automatically acquire data. Refer to the Auto-Polling section for
more information.
Mode Use Auto-Poll Use Command List
N (None) N Y
M (Multi-drop) Y Y
P (Point-to-Point) Y Y
When configured for Point-to-Point communication, the channel will automatically
poll data from the connected slave address 0.
When configured for Multi-drop, the channel will automatically poll data from the
connected slaves in the network (address 1 to 15). Refer to the Auto-Polling
section for more information about auto-poll mode.
User-configured commands can be issued on each channel to the HART
devices. Up to 99 commands can be defined for each port. Data read from the
devices is placed in the virtual database of the module, which is passed between
the module and the processor.
Any write requests or device-specific commands for the HART slave devices are
sourced with data from the virtual database, or from a configured constant data
block. Within the commands, it can be specified whether or not to use the HART
device's short or long address. If the long address is selected, the device is
polled first with short address to ask for the long one. Then, the device is polled
with the long address. The module does this processing automatically.
In a HART network, it is possible to have two masters. The module fully supports
the existence of a second master, but it can reduce the throughput on the HART
network. This facility is enabled or disabled in the module's configuration. If the
ability to have a second master on the network is disabled, then the maximum
communication throughput is achieved.