ALTUS Nexto NX3004 - Page 92

4. Configuration
84
Notes:
Setting: the number of factory default settings, and the values for the column Options, may vary
according to the data type and MODBUS function (FC).
Function Code: MODBUS (FC) functions available are the following:
Function Type
Code
Description
DEC
HEX
Access to Variables
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 coil (FC 05)
6
0x06
Write holding register (FC 06)
15
0x0F
Write multiple coils (FC 15)
16
0x10
Write holding registers (FC 16)
22
0x16
Register write mask (FC 22)
23
0x17
Read/Write holding registers (FC 23)
Table 4-50. MODBUS Functions Supported by Nexto CPUs
Scan: this parameter indicates how often the communication set for this request must be performed.
By the end of a communication will be awaited a time equal to the value configured in the field scan
and after that, a new communication will be executed.
Initial Address of the Read Data: field for the initial address of the MODBUS read data.
Read Data Size: the minimum value for the read data size is 1 and the maximum value depends on
the MODBUS function (FC) used as below:
 Read Coils (FC 1): 2000
 Read Input Status (FC 2): 2000
 Read Holding Registers (FC 3): 125
 Read Input Registers (FC 4): 125
 Read/Write Holding Registers (FC 23): 121
Read Data Range: this field shows the MODBUS read data range configured for each request. The
initial address, along with the read data size will result in the range of read data for each request.
Initial Address of the Write Data: field for the initial address of the MODBUS write data.
Write Data Size: the minimum value for the write data size is 1 and the maximum value depends on
the MODBUS function (FC) used as below:
 Write Single Coil (FC 5): 1
 Write Single Holding Registers (FC 6): 1
 Write Multiple Coils (FC 15): 1968
 Write Holding Registers (FC 16): 123
 Register Write Mask (FC 22): 1
 Read/Write Holding Registers (FC 23): 121
Write Data Range: this field shows the MODBUS write data range configured for each request. The
initial address, along with the read data size will result in the range of write data for each request.
Diagnostic Variable: The MODBUS request diagnostics configured by symbolic mapping or by
direct representation, are stored in variables of type T_DIAG_MODBUS_RTU_MAPPING_1 and
the mapping by direct representation are in 4-byte and 2-word, which are described in Table 4-51 (n
is the value configured in the Diagnostic Initial Address field in %Q).