[SI-LIST] R: starter

maybe the signal positive step is too slow and you cannot see the reflection
effects because the transmission line is too short. Try a really long
transmission line compared with the wave length
tell me if you succeed,
By
        Giovanni

-----Messaggio originale-----
Da: peter strauss [mailto:ptr_strss@xxxxxxxxx]
Inviato: mercoledì 25 maggio 2005 15.26
A: si-list@xxxxxxxxxxxxx
Oggetto: [SI-LIST] starter


Hi,
 
I am a SI starter.
 
I downloaded Pspice student and tried to model transmission line ringing. A
7474 (pspice) driving a non-lossy transmission line. No termination. output
of the transmission line is connected to another 7474 input. I also have a
1K connected to GND at the o/p of transmission line. The transmission line
shiled is connected to GND at both ends.
 
When I simulate, I see ringing only on falling edge! Why is there no ringing
on rising edge? The rising edge comes out as a capacitive rise time.
 
I tried removing the 7474 at the o/p of the transmission line - i.e.-only 1K
resisitor at the o/p. This behaves same.
 
The digital IO model seems balanced on drive circuit. approx. 100OHM in both
low and high.
 
Can anybody lead me in the right direction of thinking?
 
Thanks,
peter
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