Rockwell Automation 1756-IH16ISOE ControlLogix Sequence of Events Module - Manual (Page 21)

Publication 1756-UM528A-EN-P - April 2004
How Does the Sequence of Events Module Operate in a ControlLogix System? 2-5
Figure 2.1
Hardware
delay
Filter
delay
ASIC
delay
User configurable
0 - 50ms
Up to 25
µs
Signal applied
at the RTB
Signal
sent to
backplane
1756-IB16ISOE
For OFF to ON:
• 10µs - nominal
• 20µs - maximum
For ON to OFF:
• 25µs - nominal
• 50µs - maximum
42701
1756-IH16ISOE
For OFF to ON:
• 10µs - nominal
• 20µs - maximum
For ON to OFF:
• 50µs - nominal
• 75µs - maximum
CST captured here
Digital
signal
processor
Scan
time
Typically
175 µs - FIFO
mode or
625 µs - CST
Per Point
mode
EXAMPLE
Many factors (e.g. voltage, operating temperature, if
the module is turning ON or OFF) affect the signal
propagation delay on a module. But a nominal delay
time can be estimated.
For example, if you are turning ON a
1756-IB16ISOE module at 24V dc in 25°C
conditions, the signal propagation delay is
affected by:
• hardware delay to energize the module
(nominally 10
µS on this module)
• user-configurable input filter time (0 to 50ms)
• firmware scan time (up to 25µs)
• ASIC delay (175µs - FIFO mode/625µs - CST Per
Point mode)
In the typical case scenario (i.e., filter time of 0ms),
the module has a signal propagation delay of
approximately 210
µs (FIFO) to 660µs (CST Per
Point).