User Manual For - CONTROLLER/DATA RECORDER MultiCon CMC-99/141
Input list
and
Output list
in the
Device channels
parameter block of the device
(see above in this Chapter). If the user creates a block of registers to read / preset in
which there were no registers appearing on the Input list and Output list in the
Device channels
parameter, this device in case of:
-
read
- the read whole register block and registers undefined in the Input list
menu will not be visible in the Logical channel in the Modbus mode which
cannot be read either data from these registers and to use these registers to
control and regulate the process,
-
preset
- will send the frame to preset the entire block of registers and
registers not defined in the
Output list
will not appear on the
External
output
menu
Warning! In this case a random value of these registers will be sent to Slave
device, uncontrolled by the user.
7.15.4. Modbus - Example of Modbus protocol configuration in the device
The Modbus protocol sends data in the floating point format. In this connection
the user should keep in mind that transmitted and received values using
the Modbus protocol can be slightly different. This situation can happen when
a decimal value can not be represented as floating point numbers, or when the least
significant digit is eight orders of magnitude smaller than the 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 (e.g. a temperature
converter). We read register 1 which contains temperature, register 2 is a status register,
register 3 is a decimal point register. The device has addresses 1 and 8. To set the Modbus
configuration for the same devices, the 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
(in accordance with
Fig. 7.154
).
248
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