146 Rockwell Automation Publication ICSTT-RM448M-EN-P - February 2021
protocol which provides a safety layer for the Ethernet network making it a
"Black Channel".
SNTP Simple Network Time Protocol. Used for synchronizing the clocks of computer
systems over packet-switched, variable-latency data networks.
structured text A high level IEC 61131-3 language with syntax similar to Pascal. Used mainly to
implement complex procedures that cannot be expressed easily with graphical
languages.
synchronous A data communications term describing a serial transmission protocol. A pre-
arranged number of bits is expected to be sent across a line per second. To
synchronise the sending and receiving machines, a clocking signal is sent by
the transmitting computer. There are no start or stop bits.
T
TA See 'termination assembly'.
target An attribute of a 'configuration' which describes characteristics of the
AADvance controller on which the configuration will run. Includes
characteristics such as the memory model and the sizes of variable types for
the controller.
TCP Transmission control protocol. One of the core protocols of the Internet
Protocol suite. It provides reliable, ordered delivery of a stream of bytes from a
program on one computer to another program on another computer.
Common applications include the World Wide Web, e-mail and file transfer
and, for an AADvance controller, MODBUS communications over Ethernet.
termination assembly A printed circuit board which connects field wiring to an input or output
module. The circuit includes fuses for field circuits. The board carries screw
terminals to connect field wiring to the controller, and the whole assembly
clips onto the 9300 I/O base unit.
TMR Triple modular redundant. A fault tolerant arrangement in which three
systems carry out a process and their result is processed by a voting system to
produce a single output.
TÜV certification Independent third party certification against a defined range of international
standards including IEC 61508.
U
U Rack unit. A unit of measure used to describe the height of equipment
intended for mounting in a standard rack. Equivalent to 44.45mm (1-¾ inches).
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