F.10 Function block RTC (Real Time Clock)
The RTC function block shown below sets the output CDT to the input value PDT at the next evaluation
of the function block following a transition from 0 to 1 of the IN input. The CDT output of the RTC
function block is undefined when the value of IN is 0.
Function block RTC (Real Time Clock)
PDT = Preset date and time,
loaded on rising edge of IN
CDT = Current date and time,
valid when IN=1
Q = copy of IN
+-------+
| RTC |
BOOL---|IN Q|---BOOL
DT-----|PDT CDT|-----DT
+-------+
F.11 Function block ALRM_INT
This function block type provides simple high and low level alarming for an input of type INT and
illustrates the use of the VAR_OUTPUT declaration with functions. The function output is TRUE if a high
or low threshold is exceeded, and separate outputs are provided for the high- or low-level alarm
conditions.
Copyright International Electrotechnical Commission
Provided by IHS under license with IEC
Not for Resale
No reproduction or networking permitted without license from IHS
--``````-`-`,,`,,`,`,,`---
61131-3
IEC:2003(E)
– 207 –
+----------+
| ALRM_INT |
IN----|INT |---BOOL
THI---|INT HI|---BOOL
THL---|INT LO|---BOOL
+----------+
+---+
IN---| > |---+-----------------HI
THI--| | | +----+
+---+ +--| OR |---ALRM_INT
+---| |
+---+ | +----+
IN---| < |--+------------------LO
THL--| |
+---+
FUNCTION ALRM_INT : BOOL
VAR_INPUT
INT : IN ;
INT : THI ; (* High threshold *)
INT : TLO ; (* Low threshold *)
END_VAR
VAR_OUTPUT
HI: BOOL; (* High level alarm *)
LO: BOOL; (* Low level alarm *)
END_VAR
HI := IN > THI ;
LO := IN < THL ;
ALRM_INT := THI OR THL ;
END_FUNCTION
Copyright International Electrotechnical Commission
Provided by IHS under license with IEC
Not for Resale
No reproduction or networking permitted without license from IHS
--``````-`-`,,`,,`,`,,`---
– 208 –
61131-3
IEC:2003(E)
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