User Manual For - CONTROLLER/DATA RECORDER MultiCon CMC-99/141
7.15.4.
Modbus - Example of Modbus protocol configuration in the device
Modbus protocol sends data in floating point format. In this connection user should
keep in mind that transmitted and received values using Modbus protocol, can be
slightly different. This situation can happened when decimal value can not be
represented as floating point numbers, or when the least significant digit is eight
orders of magnitude smaller than most significant digit.
7.15.4.1.
Input configuration of Modbus protocol in MASTER mode
See also:
Chapter 7.15.3. Modbus - MASTER mode
Task:
The task is to configure a logical channel to read Slave registers (eg temperature
converter). We read register 1 which contains temperature, register 2 is a status register,
register 3 is a decimal point register. The devices has addresses 1 and 8. To set Modbus
configuration for the same devices, Modbus template can be helpful, which will be created in
this task.
Solution:
First configure the device then connect the SLAVE device to the MultiCon
Fig. 7.129. Connection diagram for the Modbus port MB1
Description of the register of SLAVE device shown in the
217
Power supply
(depending on version)
1
2
8
5
6
7
3
4
SERVISE
+24V DC ±5%
(
I
max. = 200mA)
digital input
0/15..24V DC
RS-485
GND
GND
A+
B-
isolated
Master
Device
Slave device 1
Slave address: 1
Register: 1h
Register: 2h
Register: 3h
Baud rate: 9600 bit./sek.
Device name:Temp. converter
Registers:
Modbus settings:
Slave device 2
Slave address: 8
Register: 1h
Register: 2h
Register: 3h
Baud rate: 9600 bit./sek.
Device name:Temp. converter
Modbus settings:
Registers:
GND
B-
A+
Port MB1
i
