Honeywell HC900 - OFDT off Delay Timer Function Block

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