ATI Model F12/D Gas Transmitter Part 4 – Operation
69
O&M Manual (Rev-H)
HART Find Device
Selecting Find-Me presents a special page that remains until the master device issues a “Find Device”
command to the transmitter, at which point, line 1 of the display changes from “FIND ME ARMED” to
“DEVICE FOUND”.
Figure 93. Hart Find-Device Display
Modbus
The following applies to transmitters that have an RS232 or RS485 COM interface and Modbus firmware
options. The RS232 and RS485 option is NOT INTENDED for use in Hazardous Locations.
Modbus is a master/slave protocol that supports a single master, and up to 247 slave devices on a
common bus. The RS485 interface physically limits this number to 32 (1 master, 31 slaves), and RS232
restricts communication to a master and a single slave. Note that the 4-20mA output is fully functional
even when using the transmitter’s Modbus interface.
Modbus Menu
The Modbus Menu appears by selecting Modbus from the COM Menu (pg 66).
Figure 94. Modbus Menu
This setting provides direct access the associated HART
network management setting. The value is adjustable only
when the Loop setting is FIXED, and may be adjusted between
3.5 (4mA on 2-wire power) and 22 mA.
This setting provides direct access to the associated HART
network management setting, which determines the number
of preamble characters (FF hex) transmitted at the beginning
of each message. The default value is 5, and may be set from
3 to 20. Changing this setting is not recommended.
This method places the transmitter into a mode that causes
the transmitter to respond to the Find Device command. This
is used by personnel identify transmitter in the field. The
method is describe below.
This setting controls the address to which the transmitter
responds to queries from the host (1-247, default =1).
This setting belongs to the data-link layer of the protocol and
defines the number of character bits used to frame Modbus RTU
messages. The protocol specifies the silent interval as 3.5
characters, which corresponds to 35 bit-times at 10 bits per
character. This setting is reserved for future use and changing it
is not recommended.
►Poll Addr= 1
Timeout= 35
Menu>Setup>I/O>COM>Modbus
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