Rockwell Automation 5370-CVIM2 Module - Manual (Page 485)

Chapter 9
Discrete I/O Assignments
9–22
Figure 9.15 is an example of a missed–trigger situation, in which a second
trigger signal arrives before the system is ready to process another trigger.
When this occurs, the system sets the Trigger NAK signal.
Figure 9.15 Example: Timing Relationships for Missed Trigger
TRIGGER
ACK
MODULE
READY
MODULE
READY
TRIGGER NAK goes high
because trigger 2 cannot be
processed. (Trigger 1
processing is not yet complete.)
TRIGGER NAK stays low
because trigger 3 can be
processed. (Trigger 1
processing is now complete.)
TRIGGER
NAK
Trigger
pulse #1
Trigger
pulse #2
DATA
VALID
** *
See NOTE below
TRIGGER
(Input)
Trigger
pulse #3
MISSED–TRIGGER EXAMPLE
STROBE
NOTE: If trigger pulse #2 occurs within the “debounce” time after
trigger pulse #1, it is assumed to be trigger “bounce” and is ignored.
MODULE READY goes high when system is placed
online, and stays high until it is placed offline.
*Acquisition time:
34 – 51ms, for two–field resolution;
17 – 34ms for one–field resolutions.
** Analysis time.
Typically 300 to 600 mSec
Typically 700 to 1200
mSec