Comtrol Modbus TCP Quick Start Manual de usuario descargar pdf (Pagina 47)

DeviceMaster UP Modbus/TCP Quick Start: 2000477 Rev. G Configuring Read/Write Raw/ASCII Devices - 47

Configuring Read/Write Raw/ASCII Devices

Transmit messages have the following characteristics:

• All data is transferred in 16 bit words.

• If operating in Tx (From PLC) Transfer Mode of Master (Poll the PLC): The sequence number must be

incremented when there is new data to transmit.

• If operating in Tx (From PLC) Transfer Mode of Slave (PLC Writes): The sequence number must be

incremented when there is new data to transmit only if the Disable Tx Sequence Number Check is not

selected.

• The data length field indicates the number of valid bytes contained in this message.

• The actual length of the message received from a PLC may contain extra, unused data.

• Unused data is ignored.

• A request for transmit data returns the last transmit data message.

Read/Write Raw/ASCII Ethernet Devices

Read/write raw/ASCII

Ethernet devices use the

Ethernet Device

Configuration page to:

• Allow connections

between an Ethernet

device, such as a

barcode scanner, RFID

reader, or weigh scale,

and a PLC and/or an

application.

• Raw/ASCII data is the

only supported data

type.

• The Ethernet device

must support Ethernet

TCP socket

connections.

Note: The PLC and

applications can

both communicate to the Ethernet device, but they cannot communicate directly to each other.

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Comtrol Modbus TCP Quick Start Manual de usuario Pagina 47