192 SI-Ethernet User Guide
Issue: 1
Non-crossover lead: See Patch lead.
Non-cyclic (explicit) data: Data that is requested or sent as required and not on a
regular basis. Sometimes referred to as “Explicit data”.
Octet: A collection of 8 binary digits which form a byte.
Patch lead: A network cable where the terminal connections at one end of the cable are
connected straight through to the other end on a pin to pin basis. Normally used to
connect a network device to a network switch.
PC: Personal Computer.
PDU: Protocol Data Unit. This is the main Modbus message telegram, to which is added
the MBAP header to form the complete Modbus telegram.
PLC: Programmable Logic Controller.
Poll rate: The rate at which cyclic data is sent and received on the network.
Polled data: See Cyclic data.
Router: A device that is used to connect different networks or subnets, in a similar way
to a firewall, however a router generally allows significantly less control of the data.
RPI: Requested Packet Interval. Specifies the expected time for the device to respond
to a request.
Scan rate: See Poll rate.
Shielding: A connection to provide additional immunity to noise used on a network
cable.
SMTP: Simple Mail Transfer Protocol. A protocol used for sending email.
SNTP: Simple Network Time Protocol. A protocol used for synchronising time over a
network.
To Next Page
Loading...
