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4/00 UDC 3300 Process Controller Product Manual 135
4.14 Communications Set Up Group
Introduction
This option allows the controller to be connected to a host computer via
RS-422/485 or Modbus protocol.
The controller looks for messages from the computer at regular intervals.
If these messages are not received within the configured shed time, the
controller will SHED from the communications link and return to stand-
alone operation. Depending on the protocol selected, the device address,
parity, and baud rate are configurable. You can also set the SHED output
mode and setpoint recall, and communication units.
Up to 99 addresses can be configured over this link. The number of units
that can be configured depends on the protocol chosen:
• RS-422/485—15 drops maximum
• Modbus—15 drops (or 31 for shorter link length) maximum
Communications
group prompts
Table 4-13 lists all the function prompts in the Communications Set Up
group and their definitions.
Table 4-13 Communications Group Definitions
Lower Display
Prompt
Upper Display
Range of Setting
or Selection
Parameter
Definition
ComSTATE
DISABL
MOD3K
MODBUS
RS422
COMMUNICATIONS SELECTION
DISABLE—Disables the communications option.
MB3K—Allows the UDC3300 to emulate the UDC3000A
Modbus protocol.
MODBUS—Allows Modbus RTU communication prompts.
RS-422/485—Allows RS422/485 ASCII communication
prompts.
Com ADDR
1 to 99 COMMUNICATIONS STATION ADDRESS (LOOP 1)—
This is a number that is assigned to a controller that is to
be used with the communications option. This number will
be its address.
ComADDR2
1 to 99 COMMUNICATIONS STATION ADDRESS (LOOP 2)—
This is a number that is assigned to a controller that is to
be used with the communications option. This number will
be its address. When ComSTATE = MODBUS,
ComADDR2 = Com ADDR.
ATTENTION
If RS-422/485 addresses on both loops are
the same, then only Loop 1 will respond.
SHED ENAB
DISABL
ENABLE
SHED ENABLE—Disables/enables shed functionaliy.
Applies to Modbus protocol only.