92 Rockwell Automation Publication ICSTT-RM406J-EN-P - February 2021
SIL Safety Integrity Level. One of four possible discrete levels, defined in IEC 61508
and IEC 61511, for specifying the safety integrity requirements of the safety
functions to be allocated to a safety-related system. SIL4 has the highest level
of safety integrity; SIL1 has the lowest.
The whole of an installation (of which the AADvance system forms a part) must
meet these requirements in order to achieve an overall SIL rating.
SNCP SNCP (Safety Network Control Protocol) is the Safety Protocol that allows
elements of an AADvance System to exchange data. SNCP is a SIL 3 certified
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 ‘project’ that describes characteristics of the AADvance
controller on which the project 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.
TÃœV certification Independent third party certification against a defined range of international
standards including IEC 61508.
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