RTC

RTC is a function block that calculates elapsed time since a given start time. On a rising edge of EN, CDT is set to PDT and starts increasing; on a falling edge, CDT is set to DT#1970-01-01-00:00:00. It can also return the current date and time by setting PDT to the current local time on the rising edge of EN.

Source checked15/15 values · 2026-10-26

Specification

1 source

Language	structured text
Code	RTC
Group	Function block
Syntax	RTC(EN:=VarBOOL1, PDT:=DT#2006-03-30-14:00:00, Q=>VarBOOL2, CDT=>VarTimeCur);
Dialect

Parameters

Name	Data type	Description
EN	BOOL	Rising edge: CDT is set to PDT and CDT starts increasing. Falling edge: CDT is set to DT#1970-01-01-00:00:00.
PDT	DT	Preset date and time
Q	BOOL	TRUE as long as CDT is counting
CDT	DT	Date and time, elapsed since PDT

Study notes

With PDT set to DT#1970-01-01-00:00:00 or left unconnected, RTC can be used as an operation hour counter.
To return the current date and time, set PDT to the current local time on the rising edge of EN.

Safety

The counter overflows on 7 February 2106.