counters |
Instructions that allow PLCs to keep track of actions or events, such as the number of items placed in a container or the number of times a motor or machine has turned on, and to respond when a specific count is reached. |
CTD counter |
Count down counter. An IEC counter instruction that counts down by 1 when the count down parameter (CD) transitions from 0 to 1. |
CTU counter |
Count up counter. An IEC counter instruction that counts up by 1 when the count up parameter (CU) transitions from 0 to 1. |
CTUD counter |
Count up and down counter. An IEC counter instruction that counts up by one on a 0 to 1 transition of CU and counts down by 1 on a 0 to 1 transition of CD. |
data block |
DB. A memory structure used in Siemens PLC user programs to store data for a code block. All of the program blocks in the user program can access the data in a global DB, but an instance DB stores data for a specific function block (FB). |
data type |
A definition that specifies both the bit size of a data element as well as how the bit string is to be interpreted. |
DB |
Data block. A memory structure used in Siemens PLC user programs to store data for a code block. All of the program blocks in the user program can access the data in a global DB, but an instance DB stores data for a specific function block (FB). |
decrements |
Counts down or decreases. |
FBD |
Function block diagram. A graphical programming language defined in part 3 of the IEC 61131 standard. |
function block diagram |
FBD. A graphical programming language defined in part 3 of the IEC 61131 standard. |
IEC 61131 |
A standard of the International Electrotechnical Commission that defines programmable logic controller capabilities. Part 3 of this standard (IEC 61131-3) defines PLC programming languages. |
IEC counters |
PLC counter instructions that conform to the descriptions provided in IEC 61131. |
IEC timers |
PLC timer instructions that conform to the descriptions provided in IEC 61131. |
Int |
Signed integer. A 16-bit (1 word) data type that can represent an equivalent decimal range from -32,768 to +32,767. |
LTime data type |
A 64-bit data type available for use in SIMATIC S7-1500 PLCs. This data type is used with IEC timers for preset time (PT) and elapsed time (ET) values when these values exceed the range of the Time data type. |
OB |
Organization block. A program structure that links the user program to the PLC operating system. A variety of OBs are used in Siemens PLC programs. Some OBs have predefined behaviors and start events, but also can be created with custom start events. |
OR function |
A PLC instruction that provides a 1 at the output of the instruction if one or more of the inputs to the instruction is a 1. |
organization block |
OB. A program structure that links the user program to the PLC operating system. A variety of OBs are used in Siemens PLC programs. Some OBs have predefined behaviors and start events, but also can be created with custom start events. |
PT instruction |
Preset timer instruction. An IEC timer instruction that loads a preset time value to the specified timer. |
RT instruction |
Reset timer instruction. An IEC timer instruction that resets the specified timer. |
set reset flip-flop |
SR flip-flop. A PLC instruction that sets the output parameter Q to 1 when the set input transitions from 0 to 1 and resets Q to 0 when the reset input transitions from 0 to 1. The reset input is dominant over the set input, so, if both inputs are 1 at the same time, Q is 0. |
signed double integer |
Dint. A 32-bit (1 double word) data type that can represent an equivalent decimal range from -2,147, 483, 648 to +2,147, 483, 647. |
signed integer |
Int. A 16-bit (1 word) data type that can represent an equivalent decimal range from -32,768 to +32,767. |
SIMATIC counter |
PLC counter instruction developed for use in Siemens SIMATIC PLCs prior to the development of the IEC 61131 standard. These instructions are still widely used. |
SIMATIC timer |
PLC timer instruction developed for use in Siemens SIMATIC PLCs prior to the development of the IEC 61131 standard. These instructions are still widely used. |
Time data type |
A 32-bit data type used by IEC timers for preset time (PT) and elapsed time (ET) values. Time data is stored as a signed double integer interpreted as milliseconds. |
timers |
Instructions that allow PLCs to control and monitor time-dependent aspects of machines and processes. |
TOF timer |
Off-delay timer. An IEC timer instruction that sets the output parameter (Q) to on and then resets the output to off after a preset time delay. |
TON timer |
On-delay timer. An IEC timer instruction that sets the output parameter (Q) to on after a preset time delay. |
TONR timer |
On-delay retentive timer. An IEC timer instruction that sets the output parameter (Q) to on after a preset time delay. The elapsed time can be accumulated over multiple timing periods. The reset parameter (R) is used to reset the elapsed time. |
TP timer |
Pulse timer. An IEC timer instruction that generates a pulse with a preset time width. |
UInt |
Unsigned integer. A 16-bit (1 word) data type that can represent an equivalent decimal range from 0 to 65,535. |
unsigned integer |
UInt. A 16-bit (1 word) data type that can represent an equivalent decimal range from 0 to 65,535. |
unsigned short integer |
USInt. An 8-bit (1 byte) data type that can represent an equivalent decimal range from 0 to 255. |
USInt |
Unsigned short integer. An 8-bit (1 byte) data type that can represent an equivalent decimal range from 0 to 255. |