Reception of invalid commands, Reception of commands with illegal fields, Response to a preset single register command – Flowserve L75 Series Electric Actuator User Manual
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L75 Series Electric Actuator — Modbus RTU FCD LMAIM7502-00 – 07/05
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Preset Single Register Command (06)
This command sets the state of a specific motion control circuit by writing values to register 40,001.
By writing a value of 256 (dec) to the register, the CCW motion control circuit is activated. By writing a
value of 512 (dec) to the register, both the CCW and CW motion control circuits are deactivated. Finally,
writing a value of 768 (dec) to register 40,001 initiates the CW motion control circuit. Other data values
will return an exception response. Broadcast is not supported.
Example: “Direct actuator #1 to stop operation in either the CW or CCW direction”
Field Name
Example
Actuator Address
01
Function (Force Single Coil)
06
Coil Address (High)
00
Coil Address (Low)
00
Force Data (High)
02
Force Data (Low)
00
CRC Error Check (LS byte)
88
CRC Error Check (MS byte)
AA
The bytes sent (in hex) to the actuator in the above example would be: 01, 06, 00, 00, 02, 00, 88, AA
Response to a Preset Single Register Command
The normal response is an echo of the original command, returned after the register value is written.
Field Name
Example
Actuator Address
01
Function (Force Single Coil)
06
Coil Address (High)
00
Coil Address (Low)
00
Force Data (High)
02
Force Data (Low)
00
CRC Error Check (LS byte)
88
CRC Error Check (MS byte)
AA
The bytes sent (in hex) back to the master in the above example would be: 01, 06, 00, 00, 02, 00, 88, AA
Reception of Invalid Commands
A Modbus command is considered invalid if any of the following conditions is true:
The computed CRC value does not match the CRC in the received message.
The message is not addressed to the actuator.
The message is a broadcast message.
In any of the above situations, the actuator will discard the invalid message and no error response will
be returned. The master should detect a timeout and reissue the command.
Reception of Commands with Illegal Fields
If a command is received with a field containing an illegal value, the actuator will reply with an Exception
Response (see the Modbus Exception Responses section below). No exception response will be given if
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