Rockwell Automation Publication ICSTT-RM448J-EN-P - April 2018
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Glossary
SIF
Safety Instrumented Function. A form of process control that performs
specified functions to achieve or maintain a safe state of a process when
unacceptable or dangerous process conditions are detected.
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 '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.
