5. CONFIGURATION
Data Type Size [bits] Description
Coil 1 Digital output that can be read or written.
Input Status 1 Digital input (read only).
Holding Register 16 Analog output that can be read or written.
Input Register 16 Analog input (read only).
Table 103: MODBUS data types supported by Nexto CPUs
Code
DEC HEX Description
1 0x01 Read Coils (FC 01)
2 0x02 Read Input Status (FC 02)
3 0x03 Read Holding Registers (FC 03)
4 0x04 Read Input Registers (FC 04)
5 0x05 Write Single Coil (FC 05)
6 0x06 Write Single Holding Register (FC 06)
15 0x0F Write Multiple Coils (FC 15)
16 0x10 Write Multiple Holding Registers (FC 16)
22 0x16 Mask Write Holding Register (FC 22)
23 0x17 Read/Write Multiple Holding Registers (FC 23)
Table 104: MODBUS Functions Supported by Nexto CPUs
Independent of the configuration mode, the steps to insert an instance of the protocol and configure the Ethernet interface
are equal. The remaining configuration steps are described below for each modality.
Add one or more instances of the MODBUS Ethernet client or server protocol to Ethernet channel. To perform this
procedure, refer to the section Inserting a Protocol Instance.
Configure the Ethernet interface. To perform this procedure, see section Ethernet Interfaces Configuration.
5.5.8. MODBUS Ethernet Client
This protocol is available for all Nexto Series CPUs on its Ethernet channels. When selecting this option at MasterTool
IEC XE, the CPU becomes a MODBUS communication client, allowing the access to other devices with the same protocol,
when it’s in execution mode (Run Mode).
There are two ways to configure this protocol. The first one makes use of direct representation (%Q), in which the variables
are defined by your address. The second one, through symbolic mapping, where the variables are defined by your name.
The procedure to insert an instance of the protocol is found in detail in the MasterTool IEC XE User Manual – MU299609
or on Inserting a Protocol Instance section.
5.5.8.1. MODBUS Ethernet Client Configuration via Symbolic Mapping
To configure this protocol using Symbolic Mapping, it’s necessary to execute the following steps:
Configure the general parameters of MODBUS protocol client, with the Transmission Control Protocol (TCP) or RTU
via TCP.
Add and configure devices by setting IP address, port, address of the slave and time-out of communication (available on
the Advanced Settings button of the device).
Add and configure the MODBUS mappings, specifying the variable name, data type, data initial address, data size and
variable that will receive the quality data.
Add and configure the MODBUS request, specifying the desired function, the scan time of the request, the initial address
(read/write), the size of the data (read/write), the variable that will receive the data quality and the variable responsible
for disabling the request.
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