NI PXI 6552 Dinamic generation with external sample clock does not work

[Abelardo]

I am using the NI PXI 6552 to generate a digital signal, as
clock I want to use an external source that I drive in the board via de CLK IN SMB
connector. Always I got the same error (cod: 1074115898) from the ?Write? VI
block, the reason is that there is not clock signal or is not detected.




I tried the example ?Dynamic Generation with External Sample
CLK? and I have the same error.




The clock signal is in 3,3V logic. The same clock signal
works to acquire via the STROBE pin. I have scoped the CLK and the shape is
quite ok. I have tried the two possible impedances for the CLK input also.




I found one respond (http://digital.ni.com/public.nsf/allkb/884C5A76BA1A474E8625717A0068AA09)
about strange behavior of CLK IN but the proposed solution does not help in my
situation.




 Does somebody have an idea about the problem?


 


Thanks,


Abe

[Ryan M]

Abe,

At what frequency are you trying to run and are you certain the clock
you are providing to the CLKIN SMB terminal is at the same rate you are
telling software?  Software makes some calculations behind the
scene based on the value you give it that may result in clocking errors
if the actual rate does not match this.  Also, can you try running
at a frequency slower and faster than 25MHz to see if you get the same
or different errors?  Have you verified that the input to CLKINSMB
meets all of the specifications outlined in the documentation? 
Since this terminal is AC coupled, the dutycycle specifications are of
particular importance.

External Sample
clock
requirements
Square Waves ?
Voltage range 0.65 Vpp to 5.0 Vpp ?
Frequency
range
NI 6552: 20 kHz to 100 MHz ?
NI 6551: 20 kHz to 50 MHz ?
Duty cycle
range
f < 50 MHz: 25% to 75%
f ? 50 MHz: 40% to 60%
?
Sine Waves ?
Voltage
range
0.65 Vpp
to 5.0 Vpp
1.0 Vpp
to 5.0 Vpp
2.0 Vpp
to 5.0 Vpp
?
Frequency
range
NI 6552:
5.5 MHz
to
100 MHz
NI 6552:
3.5 MHz to
100 MHz
NI 6552:
1.8 MHz to
100 MHz
?
NI 6551:
5.5 MHz
to 50 MHz
NI 6551:
3.5 MHz
to 50 MHz
NI 6551:
1.8 MHz
to 50 MHz
?


-Ryan M