ALTUS Nexto NX3004 - Page 103

4. Configuration
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Configuration
Description
Default
Options
Value Variable
Symbolic variable name
-
Name of a variable declared in a program or
GVL
Data Type
MODBUS data type
-
Coil (1-bit)
Input Status (1-bit)
Holding Register (16-bit)
Input Register (16-bit)
Data Start
Address
MODBUS data initial address
-
1 to 65536
Data Size
MODBUS data size
-
1 to 65536
Data Range
The data address range
configured
-
-
Table 4-59. MODBUS Mappings Configurations
Notes:
Variable Value: this field is used to specify a symbolic variable in MODBUS relation.
Data Type: this field is used to specify the data type used in the MODBUS relation.
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 4-60. Data types supported in MODBUS RTU Slave
Data Start Address: data initial address of the MODBUS relation.
Data Size: the Data Size value sets the maximum amount of data that a MODBUS relation can
access from the initial address. Thus, in order to read a continuous range of addresses, it is necessary
that all addresses are declared in a single relation. This field varies according to the configured type
of MODBUS data.
Data Range: this field shows the user the memory address range used by the MODBUS relation.
ATTENTION:
Differently from other application tasks, when a depuration mark in the MainTask is reached, the
task of a Slave MODBUS RTU instance and any other MODBUS task will stop running at the
moment that it tries to perform a writing in a memory area. It occurs in order to keep the consistency
of the memory areas data while a MainTask is not running.
MODBUS Slave Protocol Configuration via Direct Representation (%Q)
To configure this protocol using Direct Representation (%Q), you must perform the following steps:
 Configure the general parameters of MODBUS slave protocol, such as: communication times,
address and direct representation variables (%Q) to receive diagnostics and control relations.
 Add and configure MODBUS relations, specifying the MODBUS data type, direct representation
variables (%Q) to receive/write the data and amount of data to communicate.
The descriptions of each setting are listed below, in this chapter.
General Parameters of MODBUS Slave Protocol – Configuration via Direct Representation (%Q)
The general parameters, found on the home screen of MODBUS protocol configuration (Figure
4-25), are defined as: