Digi NS9750 - Manual (Page 816)

R e s e t a n d e d g e s e n s i t i v e i n p u t t i m i n g r e q u i r e m e n t s
7 9 2 N S 9 7 5 0 H a r d w a r e R e f e r e n c e
Reset and edge sensitive input timing requirements
The critical timing requirement is the rise and fall time of the input. If the rise time
is too slow for the reset input, the hardware strapping options may be registered
incorrectly. If the rise time of a positive-edge-triggered external interrupt is too slow,
then an interrupt may be detected on both the rising and falling edge of the input
signal.
A maximum rise and fall time must be met to ensure that reset and edge sensitive
inputs are handled correctly. With Digi processors, the maximum is 500 nanoseconds
as shown:
negative edge input
t
F
max = 500nsec
V
IN
= 2.0V to 0.8V
t
F
reset_n or positive edge input
t
R
max = 500nsec
V
IN
= 0.8V to 2.0V
t
R