Honeywell HC900 - ONDT on Delay Timer Function Block

Function Blocks
ONDT On Delay Timer Function Block
Revision 11 HC900 Hybrid Control Designer Function Block Reference Guide 225
2/07
ONDT On Delay Timer Function Block
Description
The ONDT label stands for the On Delay Timer.
This block is part of the
Fast Logic and Counters/Timers categories.
Function
Provides an ON state logic output delayed by a user specified delay time after an OFF to ON transition of
the RUN input.
An ON to OFF transition of the RUN input before the delay time has elapsed causes the timer to reset.
Transitions from OFF to ON of the input are not delayed.
• If RUN is OFF, then OUT = OFF
• If previous RUN input is OFF and RUN is ON, then TIMER = DELAY, else if timer is not zero, then
TIMER = TIMER -1.
• If RUN is ON and TIMER is 0, then OUT = ON (delay time has timed out).
Timing Diagram
On Delay
1
0
1
0
Run
Input
Output
Input
RUN
= Logic Input
Output
OUT
= Logic Output