Specifications

Functional Overview
ProLinx Communication Gateways, Inc. 11
HART Master Protocol Drive Manual
August 17, 2004
1.2.2.1 Multidrop Mode
Important: If the HART device address is between 1 and 15, you must configure the
channel for multidrop mode.
If the unit is set for multidrop mode, the module will poll each unit attached to the channel
starting with polling address 1. The parameter MAX DEVICE COUNT in the configuration
determines the maximum slave address number to be polled in multidrop mode. For
example, if the MAX DEVICE COUNT parameter is set to 3, the channel will poll for
polling addresses 1, 2, and 3. It is important when assigning the device polling
addresses for instruments on a channel to start with 1 and successfully increase the
value by one until the last instrument is assigned an address. If you set the MAX
DEVICE COUNT parameter to 2, and assign the two instruments addresses 1 and 15,
the polling address 15 will never be used (only addresses 1 and 2). Therefore, the
second instrument will never be polled and will be in communication failure. Up to 15
instruments can be assigned to a single channel (polling address 1 to 15).
If the module is configured for multidrop auto-polling (Auto-Poll Code = M), the following
diagram applies:
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•
ProLinx
HART Driver
Hart
Device
Address 1
Hart
Device
Address 4
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•
Hart Device
Address 15
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