S - Z

safe state

The condition that an output module maintains in the event of a network communication error, or when the controller enters the program mode. When either of these situations occur, the outputs automatically switch to the configured state (for digitals) or to the value (for analogs).

safety accuracy

The accuracy of an analog signal guaranteed to have no dangerous faults. The signal is declared faulty when drifting outside the safety range.

safety critical state

A faulted condition preventing the execution of a process demand.

scope

The level at which tags and routines may be created. They can be created at the controller level (accessible to all routines), or the program level (accessible to only the routines within a single program).

security state

The indication of the level of access control that is applied to a given resource; such as a controller, a program organization unit, or a target.

sequential program

A program that executes according to the dynamic behavior of the programming language and SFC languages, with a time variable explicitly synchronizing operations. A sequential program gives order to operations of a process and conditions between operations.

sequential function chart (SFC)

A sequential function chart (SFC) is a flowchart that controls your machine or process. An SFC uses steps and transitions to perform specific operations or actions.

short integer (SINT)

Indicates the data type is a signed integer 8-bit format. Basic type that can be used to define a a variable, a parameter or a controller.

Safety Instrumented Function (SIF)

A process control that performs specified functions to maintain a safe state for a process when detecting unacceptable or dangerous process conditions.

Safety Integrity Level (SIL)

Defines the safety integrity performance requirements for a safety instrumented function (SIF). There are four possible SIL levels, defined in IEC 61508 and IEC 61511, for specifying the performance requirements of the safety functions allocated to a safety-related system. Each level corresponds to a range of target likelihood of failures of a safety function. SIL4 has the highest level of safety integrity while SIL1 has the lowest.

simplex module

A processor or I/O module in a single configuration suitable for non-safety to low demand SIL2 requirements.

simulation mode

Mode in which virtual machines execute the code of individual controllers and the Windows platform performs aspects such as program execution.

Safety Network Control Protocol (SNCP)

A safety protocol enabling controllers to exchange data within a Ethernet network system.SNCP is a SIL3 certified protocol providing a safety layer for Ethernet networks.

Simple Network Time Protocol (SNTP)

A simplified version of Network Time Protocol (NTP) used to synchronize computer clocks on a network.

spurious trip rate

The rate at which safety functions are activated without the presence of a specified process demand. Spurious trip level (STL) is a discrete level for specifying the spurious trip requirements of safety functions to be allocated to safety systems.

status Booleans

Boolean variable giving the status information about a signal, process, action, or component. A boolean can be TRUE (1) or FALSE (0).

stencil

A group of shapes.

step

A basic graphic component representing a steady situation of the process. A step is referenced by a name. The activity of a step is used to control the execution of the corresponding actions. Actions are used to perform functions such as turning outputs on or off in a step.

STRING

Data type used to denote a character string. Basic type that can be used to define a variable, a parameter, or a controller.

structure

A data type composed of a sequence of members. A structure tag occupies a contiguous block of memory in the controller with each member in sequence in memory.

sub-program

A program called by a parent program. A sub-program is also called a child program.

symbol table

The file corresponding to the variables and function blocks defined for a controller. This file is downloaded onto the target. The symbol table is set to one of two formats: complete table or reduced table. The complete table contains all defined variables, whereas, the reduced symbol table only contains the names of variables having a defined address cell.

synchronous

Data communications term describing a serial transmission protocol. A pre-arranged number of bits is expected to be sent across a line each second. To synchronize the sending and receiving machines, a clocking signal is sent by the transmitting computer. Synchronous communications do not use start and stop bits.

synchronizing secondary

A chassis that has a partner primary control chassis, and is currently attempting to achieve synchronization. In this state of readiness, a secondary control chassis cannot assume the primary state.

system events

Events occurring on the development platform. Such events can be logged using the Events Logger and viewed using the Events Viewer.

system variable

System variables hold the current values of all system variables for a project. You can read from or write to system variables. These variables are defined in the dsys0def.h file. For example, the current cycle time is a system variable that can only be read by a program.

target

The hardware platform onto which you download an application. Includes characteristics such as the memory model and variable types.

TCP/IP

Transmission Control Protocol/Internet Protocol. A transport layer protocol and a network layer protocol developed by the Department of Defense. This is a commonly used combination for communication within networks and across internetworks.

TIMER

A structure data type that contains status and control information for timer instructions.

Triple Modular Redundant (TMR)

A fault tolerant arrangement in which three systems (modules) complete a process and the result is determined by a voting system to provide one output, also called a

Triplicated Module

.

token (SFC)

Graphical marker used to show the active steps of an SFC program.

top level program

Program put at the top of the hierarchy tree. A top level program is activated by the system.

transition

The change of state from an Off to On condition or vice versa.

transition step

A basic graphic component representing the condition between different steps. A transition step is referenced by a name. A boolean condition is attached to each transition step.

trigger cycles

A project property indicating whether a resource cycle executes according to a defined cycle timing.

triplicated module

One of three processors or I/O modules arranged in parallel configuration. The parallel arrangement enables three paths for command signals and I/O data and increases their fault tolerance, also called

Triple Modular Redundant

.

TÜV Certification

Independent third-party certification against a range of international standards, including IEC 61508.

unsigned double integer (UDINT)

Unsigned double integer 32-bit format. Basic type that can be used to define a variable, a parameter or a controller.

unsigned integer (UINT)

Unsigned integer 16-bit format. Basic type that can be used to define a variable, a parameter or a controller.

unsigned long integer (ULINT)

Unsigned integer 64-bit format. Basic type that can be used to define a variable, a parameter or a controller.

unsigned short integer (USINT)

Unsigned integer 8-bit format. Basic type that can be used to define a variable, a parameter or a controller.

user-defined data types

Types that the user can define using basic data types or other user-defined data types. User-defined data types can be arrays or structures.

user-defined function block

A user defined program that can be packaged into an instruction block.

variable

A unique identifier of elementary data that is used in the programs of a project.

variable name

A unique identifier for a storage location containing information used in exchanges between projects.

voting system

A redundant system (m out of n) requiring at least m of the n channels to be in agreement before the system can take action.

wiring

The property of a variable indicating the I/O channel to which the variable is wired.

WORD

A storage location in memory consisting of a group of 16 bits or 2 bytes. A grouping or number of bits in a sequence that is treated as a unit.

write protected

The indication of whether the variable can be written.