Grundfos CIU 250, Instructions Manual

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12. Modbus telegram examples

12.1 Diagnostics: return query data

This function is useful to ensure that the communication path and 
slave configuration are correct. It will echo the request in the 
response.
In the example, slave address 0x01 is used.

Request from master to slave

Example of response from slave to master

If there is no response from the slave, see section 

9. Data item 

overview

.

12.2 Reading the CIM configuration register block

This section shows how to read the first four registers of the 
CIM configuration register block.
In the example, slave address 0x01 is used.

Request from master to slave

Example of response from slave to master

If there is no response from the slave, see section 

9. Data item 

overview

.

12.3 Tripping the MP 204 

This section shows how to set the control bit that trips the 
MP 204.
In the example, slave address 0x01 is used.
To trip the MP 204, the ControlRegister (register address 00101, 
bit 1) must be raised.
Hence the value to set is 0b0000000000000010 = 0x0002.

Request from master to slave

Example of response from slave to master

If there is no response from the slave, see section 

9. Data item 

overview

.

12.4 Resetting an alarm

This section shows how to set the control bit that resets MP 204 
alarms.
In the example, slave address 0x01 is used.
To reset an alarm, the ControlRegister (register address 00101, 
bit 0) must be raised.
Hence the value to set is 0b0000000000000001 = 0x0001.

Request from master to slave

Example of response from slave to master

If there is no response from the slave, see section 

9. Data item 

overview

.

Note

CRC fields are not shown in the following 
examples.

Note

The Modbus data model states that registers 
numbered X are addressed in telegrams as X - 1, 
e.g. register 00104 (setpoint) is addressed as 
00103 in a Modbus telegram.

Field

Value

Description

Slave address

0x01

-

Function code

0x08

Diagnostics

Subcode

0x00

Echo request

Data

0xAB

Test data

Data

0xCD

Test data

Field

Value

Description

Slave address

0x01

-

Function code

0x08

Diagnostics

Subcode

0x00

Echo request

Data

0xAB

Test data

Data

0xCD

Test data

Field

Value

Description

Slave address

0x01

-

Function code

0x04

Read input registers

Start address HI

0x00

Start address
= 0x0001

Start address LO

0x00

Quantity HI

0x00

Number of registers
= 0x0004

Quantity LO

0x04

Field

Value

Description

Slave address

0x01

-

Function code

0x04

Read input registers

Byte count

0x08

8 bytes follow

00001 HI

0x00

SlaveMinimumReplyDelay
= 0x000A

00001 LO

0x0A

00002 HI

0x00

RegisterOffset
= 0x0000

00002 LO

0x00

00003 HI

0x00

Reserved value
= 0x0000

00003 LO

0x00

00004 HI

0x00

ModbusBitRate
= 0x0004

00004 LO

0x04

Field

Value

Description

Slave address

0x01

-

Function code

0x06

Write single register

Start address HI

0x00

ControlRegister address
= 00101 (0x0065)

Start address LO

0x64

Value HI

0x00

ControlRegister value
= 2 (0x0002)

Value LO

0x02

Field

Value

Description

Slave address

0x01

-

Function code

0x06

Write single register

Start address HI

0x00

ControlRegister address
= 00101 (0x0065)

Start address LO

0x64

Value HI

0x00

ControlRegister value
= 2 (0x0002)

Value LO

0x02

Field

Value

Description

Slave address

0x01

-

Function code

0x06

Write single register

Start address HI

0x00

ControlRegister address
= 00101 (0x0065)

Start address LO

0x64

Value HI

0x00

ControlRegister value
= 1 (0x0001)

Value LO

0x01

Field

Value

Description

Slave address

0x01

-

Function code

0x06

Write single register

Start address HI

0x00

ControlRegister address
= 00101 (0x0065)

Start address LO

0x64

Value HI

0x00

ControlRegister value
= 1 (0x0001)

Value LO

0x01

Subject to alterations.