Flowserve MX-100 Field Unit - Manual (Page 23)

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MX/DDC-100 Field Unit Installation and Maintenance FCD LMENIM2329-01 – 03/11
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Example of force coil command
Force coil 1 of field unit 49 ON. This will CLOSE the valve controlled by field unit 49.
Query: 31050000FF0089CA
Response: 31050000FF0089CA
Message Breakdown
Query Response
31 Slave (Field Unit) Address 31 Slave (Field Unit) Address
05 Function 05 Function
00 Coil Address Hi 00 Coil Address Hi
00 1 Coil Address Lo 00 Coil Address Lo
FF Force Data Hi FF Force Data Hi
00 2 Force Data Lo 00 Force Data Lo
89CA Error Check (CRC) 89CA Error Check (CRC)
Note 1: 0000h equals Coil Address 00000001 (field unit coil 1).
0001h equals Coil Address 00000010 (field unit coil 2).
Note 2: FF00h requests the coil to be ON. (0000h requests the coil to be OFF)
2.3.8 Modbus Function Code 06 (Preset Single Register)
This function code is used to preset a single register in the field unit. The function code is typically used to command
the DDC-100 Field Unit by writing values to the 40001 and 40002 registers. A predetermined value may be used to
open/stop/close the actuator, move the actuator to a preset position, activate/deactivate network ESD, reset the field
unit, etc.
The Modbus function code 06 is also used to command a throttling actuator to “move-to” a position of 0-100% of
open. The field unit will compare the new position value with the current position and open or close the valve to meet
the new position requirement. This is a two-step command: the first step is to write the desired position value to the
field unit register 40002, then write the value of 6656 to field unit register 40001. This sequence of commands loads
the desired position, then instructs the field unit to execute the command.
For field units containing Modbus Firmware 2.00 or greater and MX-DDC field units containing Firmware 02/01.00 or
greater, the “move-to” command may be executed with a one-step command.
Modbus function code 06 command values for controlling the DDC-100 Field Unit are given in Table 2.6. Each
command should be issued only one time for the desired field unit control. Repeated issuance of an acknowledged
command will degrade network performance.
The normal response to the (06) command is an echo of the command.
NOTE:
1) Only use values listed in T able 2.6 For field unit register 40001.
2) Field Unit Register 40002 should only be used for “move-to” position input.
3) The Host MUST issue “move-to” commands in the proper sequence. Failure to issue this two-step command
in the correct sequence will result in the field unit waiting for the proper command sequence execution before
performing the “move-to” function.
4) The “move-to” command should only be used with field units that include the position control option.
5) Do not write to Field Unit Registers 5-16.