B-38
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ni.com
Appendix B
Timing Diagrams
Example of the General Case
Calculate the setup and hold time requirements when the Gate and Source come from PFI lines
and the Gate is used in level mode.
Note
This example shows how we determine the setup and hold times for the PFI
to PFI example above (first case) using level gating.
Setup
To calculate the setup time, subtract the Source delay from the Gate delay. Use maximum
delays.
Hold
To calculate the hold time, subtract the Gate delay from the Source delay. Use minimum delays.
Output Delays
Refer to the Figure B-41 for the M Series counter/timer circuitry.
Gate Delay
PFI
to
PFI_i
22.0
ns
PFI_i to Selected Gate
6.0 ns
Selected Gate to Count Enable (Level)
18.0 ns
Count Enable Setup Time
+ 1.5 ns
47.5 ns
Source Delay
PFI
to
PFI_i
18.2
ns
PFI_i to Selected Source
+ 21.0 ns
39.2 ns
T
Setup
> 47.5 ns – 39.2 ns = 8.3 ns
Gate Delay
PFI to PFI_i
5.2 ns
PFI_i to Selected Gate
1.0 ns
Selected Gate to Count Enable (Level)
6.0 ns
Count Enable Hold Time
+ 0.0 ns
12.2 ns
Source Delay
PFI to PFI_i
6.2 ns
PFI_i to Selected Source
+ 8.0 ns
14.2 ns
T
Hold
> 14.2 ns – 12.2 ns = 2.0 ns
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