Modbus Telegram Application Examples; Diagnostics: Return Query Data; Reading The System Water Level; Reading The System Alarms - Grundfos CIM 200 Functional Profile And User Manual

13. Modbus telegram application examples

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

13.1 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. Only CIM 200 Modbus RTU supports diagnostics.
In the example, slave address 0x01 is used.
Request from the master to a slave. Note that CRC fields are not
shown.
Field Value
Slave address 0x01
Function code 0x08
Subcode 0x00
Data 0xAB
Data 0xCD
Example of a response from a slave to the master. Note that CRC
fields are not shown.
Field Value
Slave address 0x01
Function code 0x08
Subcode 0x00
Data 0xAB
Data 0xCD
If there is no response from the slave, see section
200 Modbus communication faults.

13.2 Reading the system water level

This section shows how to read and interpret the water level of
the system.
In the example, slave address 0x01 is used.
Request from the master to a slave. Note that CRC fields are not
shown.
Field Value
Slave address 0x01
Function code 0x04
Start address HI 0x01
Start address LO 0x2C
Quantity HI 0x00
Quantity LO 0x01
Example of a response from a slave to the master. Note that CRC
fields are not shown.
Field Value
Slave address 0x01
Function code 0x04
Byte count 0x02
00301 HI 0x00
00301 LO 0xDC
A system water-level value of 220 [0.01 m] equals a water level of
2.20 m.
If there is no response from the slave, see section
200 Modbus communication faults.
48

13.3 Reading the system alarms

This section shows how to read and interpret the three alarm
registers of the system. The system alarms start at Modbus
register address 210: 0x00D2.
In the example, slave address 0x01 is used.
Request from the master to a slave. Note that CRC fields are not
shown.
Field
Slave address
Function code
Start address HI
Start address LO
Quantity HI
Description
Quantity LO
-
Example of a response from a slave to the master. Note that CRC
Diagnostics
fields are not shown.
Echo request
Test data
Field
Test data
Slave address
Function code
Byte count
00210 HI
Description
00210 LO
-
00211 HI
Diagnostics
00211 LO
Echo request
00212 HI
Test data
00212 LO
Test data
If there is no response from the slave, see section
14.1.2 CIM
200 Modbus communication
When reading the three system alarm registers, the following
data becomes available:
System alarms 1: 0b 0000 0000 0000 1000
System alarms 2: 0b 0000 0000 0000 0000
System alarms 3: 0b 0000 0000 0000 0000.
As seen from the alarms table, the bit for dry-running alarm is set
in System alarms 1.
Description
-
Read input registers
Start register (00301)
= 0x012D
Number of registers
= 0x0001
Description
-
Read input registers
2 bytes follow
System water level
= 0x00DC (220)
14.1.2 CIM
Value Description
0x01 -
0x04 Read input registers
0x00
Start register (00210):
0x00D2
0xD1
0x00
Number of registers:
0x0003
0x03
Value Description
0x01 -
0x04 Read input registers
0x06 6 bytes follow
0x00
System alarms 1
0x08
0x00
System alarms 2
0x00
0x00
System alarms 3
0x00
14.1.2 CIM
faults.