Flowserve Limitorque Master Station III User Manual

Page 50

Limitorque Master Station III FCD LMENIM5001-02 – 12/13

Function code -05 is used to force a single coil. Forcing the individual coil either ON (1) or OFF (0)
will energize or de-energize a coil (digital output). Coil 1 in the field unit closes the actuator and Coil
2 opens the actuator. If the actuator is opening or closing, changing the status of coil 1 or 2 from
a value of 1 to 0 will stop the actuator (the coil will automatically be set to zero when the actuator
reaches the full open or full close position).

For function code -15 it should be noted that the coils are operated from the lowest coil number to
the highest. Forcing coil 1 or 2 OFF (0) is considered a stop command, sending a 15 command to
force two coils starting with coil 1, with coil 1 ON and coil 2 OFF, would result in the unit stopping,
since coil 2 is forced OFF after coil 1 is forced ON. To prevent inadvertent stop commands from being
issued, it is
recommended to force one coil at a time.

Available digital outputs are listed in Table 8.5. Force-coil commands should be issued only once for
the desired field unit control. Repeated issuance of an acknowledged command will degrade network
performance.

NOTE: See LMENIM2329, Installation and Operation and Maintenance Manual for MX/DDC-100 Field
Unit to configure AS and AR Relays for DDC control.

Table 8.5 - DDC-100 Coil Assignments, Modbus 05 Command Usage for Digital Outputs

Coil Number

Bit Number

Function

1 00 Close/Stop
2 01 Open/Stop
3

S1 or R1 (Opt) Latched

S2 or R2 (Opt) Latched

R3 (Opt) Latched

R4 (Opt) Latched

R5 (Opt) Latched

R6 (Opt) Latched

R7 (Opt) Latched

R8 (Opt) Latched

The normal response to the (05) command is an echo of the command.

From DCS, user must address the Master Station III and poll according to the table given in the FC
-05 configuration. See the following example of a request/response exchange between the DCS and
MSIII.

Example of force coil command
Force coil 17 of Master Station ON (This will close the valve controlled by field unit 5)
Query: 01050010FF008DFF
Response: 01050010FF008DFF

Table 8.6 - Function Code -05 Example Message Breakdown

Query

Response

MSIII Unit Address

Function

Coil Address Hi

Coil Address Hi (Coil 17; MOV5)

Coil Address Lo

Coil Address Lo (Coil 17; MOV5)

Force Data Hi

Force Data Lo

8DFF

Error Check (CRC)

8DFF

Error Check (CRC)

NOTE 1: 0010h equals coil address 0001 0001b (field unit 5, coil 1)

NOTE 2: FF00h requests the coil to be ON (0000h requests the coil to be OFF)