Page 704 - Mechanical Engineers' Handbook (Volume 2)

2 Programmable Controllers (PLCs) 695

Table 9 IEC Standard Function Blocks for Programmable
Controllers
Standard Name Function
Bistable function blocks
SR Flip-flop (set dominant)
RS Flip-flop (reset dominant)
Edge detection function blocks
R TRIG Rising edge detect
R TRIG Falling edge detect
Counter function blocks
CTU Up counter
CTD Down counter
Timer function blocks
TP One-shot (pulse) timer
TON On-delay timer
TOF Off-delay timer

Message transfer and synchronization
SEND Messaging requester
RCV Messaging responder
Source: From Ref. 3

Table 10 IEC Standard Data Types for Programmable Controllers
Keyword Data Type Bits
BOOL Boolean 1
SINT Short integer 8
INT Integer 16
DINT Double integer 32
LINT Long integer 64
USINT Unsigned short integer 8
UINT Unsigned integer 16
UDINT Unsigned double integer 32
ULINT Unsigned long integer 64
REAL Real number 32
LREAL Long real 64
TIME Duration Implementation dependent
DATE Date (only) Implementation dependent
TIME OF DAY Time of day (only) Implementation dependent
DATE AND TIME Date and time of day Implementation dependent
STRING String of 8-bit characters 8n
WSTRING String of 16-bit characters 16n
BYTE Bit string of length 8 8
WORD Bit string of length 16 16
DWORD Bit string of length 32 32
LWORD Bit string of length 64 64

Source: From Ref. 3.