Technical information

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Functions (continued)
I/O Scanning service
The I/O Scanning Service is used to manage the exchange of remote I/O states on
the Ethernet network after a simple configuration operation, with no need for special
programming.
I/O scanning is performed transparently by means of read/write requests according
to the Modbus client/server protocol on the TCP profile.
This principle of scanning via a standard protocol enables a device with the I/O
Scanning service to communicate with any device supporting Modbus TCP
messaging in server mode.
This service can be used to define:
A word zone reserved for reading inputs
A word zone reserved for writing outputs
Refresh periods independent of the PLC scan
During operation, the module:
Manages TCP connections with each remote device
Scans devices and copies the I/O to the configured word zone
Feeds back status words used to check that the service is working correctly from
the PLC application
Applies pre-configured fallback values if a communication problem occurs
A range of hardware and software products is available enabling the I/O Scanning
protocol to be implemented on any type of device that can be connected to the
Ethernet network (please consult the Modbus-IDA website:
www.modbus-ida.org.
Characteristics
Each Modicon M340 station can exchange a maximum of 100 words for writing100 words for writing
and 125 words for reading.
Maximum size in the Modicon M340 PLC that manages the service (64 stations
max.) with BMX NOE 0100/0110 and BMX NOC 0401 network modules: 2 Kwords
(input) and 2 Kwords (output).
I/O Scanning service diagnostics
I/O Scanning service diagnostics can be performed in one of five ways:
Via the application program from a specific PLC data zone
From the setup software debug screen
From the PLC system diagnostic function displayed by means of an internet
browser on a PC station
Using the TCS EAZ 01P SFE10 ConneXview diagnostic software
Using standard SNMP manager software
b
b
b
b
b
b
b
b
b
b
b
b
b
b
INPUT
OUTPUT
+
–
INPUT
OUTPUT
+
–
A
B
A
B
2
1
2 2
Word table
Read Write
Ethernet Modbus/TCP
Input words
Output words
of devices
INPUT
OUTPUT
+
–
INPUT
OUTPUT
+
–
A
B
A
B
2
1
2 2
Word table
Read Write
Ethernet Modbus/TCP
Input words
Output words
of devices
Functions (continued)
2 Device with Modbus TCP messaging in server mode
Modicon M340 automation
platform
Ethernet Modbus/TCP network
Ethernet Modbus/TCP communication services
Processors:
page 1/2
I/O:
pages 2/2 and 2/14
Software:
page 4/2
Ruggedized Modicon M340 modules:
page 6/2
1 Modicon M340 device with I/O Scanning service
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