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9. IO Scanning service
9.1. Presentation
The IO Scanning service is used to exchange I/O data between:
A controller or PLC (IO Scanner).
Devices (IO Scanning servers).
This exchange is usually performed by implicit services, thus avoiding the need to
program the controller (PLC).
The IO Scanner periodically generates the Read/Write Multiple Registers (23 = 0x17)
request.
The IO Scanning service operates if it has been enabled in the PLC and the drive.
The drive parameters assigned to IO Scanning have been selected by default. This
assignment can be modified by configuration.
The drive IO Scanning service can also be configured by the option Modbus server.
When the IO Scanning service has been enabled in the VF-MB1/S15 drive:
A TCP connection is assigned to it.
The parameters assigned in the periodic variables are exchanged cyclically between the
option and the drive.
The parameters assigned in the periodic output variables are reserved for IO Scanning.
They cannot be written by another Modbus service, even if the IO Scanner is not sending
its periodic output variables.
9.2. Periodic variables
Word No.
Output variables (written by IO Scanner) Input variables (read by IO Scanner)
0 Reserved Reserved
1 Scanner write word 1 – configurable (c001) Scanner read word 1 – configurable (c021)
2 Scanner write word 2 – configurable (c002) Scanner read word 2 – configurable (c022)
3 Scanner write word 3 – configurable (c003) Scanner read word 3 – configurable (c023)
4 Scanner write word 4 – configurable (c004) Scanner read word 4 – configurable (c024)
5 Scanner write word 5 – configurable (c005) Scanner read word 5 – configurable (c025)
6 Scanner write word 6 – configurable (c006) Scanner read word 6 – configurable (c026)
7-31 Reserved Reserved
It is possible to configure the assignment of periodic variables 1 to 6.
Please refer to "parameter" about configurable.