National Instruments NI 6221, User Manual

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Appendix B Timing Diagrams
© National Instruments Corporation B-27 M Series User Manual
• Let DFF
Setup
and DFF
Hold
be the setup and hold time of the DFF.
• Let External
Setup
and External
Hold
be the setup and hold time of the
trigger to the clock at the terminals.
Figure B-30 shows the external trigger and external clock and the trigger
delay and clock delay.
Figure B-30. External Trigger and External Clock Application
To satisfy the DFF setup and hold requirement, the following condition
must be true:
External
Setup
≥
DFF
Setup
– Cloc TriggerDelay
External
Hold
≥
DFF
Hold
+ ClockDelay – TriggerDelay
DFF
Setup
and DFF
Hold
are given by Table B-16 for AO Start and Table B-18
for AO Pause triggers.
ClockDelay is the sum of the input timing (shown in Table B-12), and
insertion timing (shown in Table B-13).
TriggerDelay is the sum of the input timing (shown in Table B-12), and
internal timing (shown in Tables B-15 and B-17).
For setup calculations, use the maximum timing parameters. For hold
calculations, use the minimum timing parameters.
For input timing, as shown in Table B-12, two numbers are given for the
maximum delay and two numbers for the minimum delay. In order to
account for the worst case skew between different input terminals, use the
range given in the input delay tables in the
Input Timing section in a way
that provides the most conservative results. For setup calculations, use the
bigger number for TriggerDelay and the smaller number ClockDelay. For
hold calculations, use the smaller number for TriggerDelay and the larger
number for ClockDelay.
DFF
D Q
Extern a l
Trigger
Extern a l
Clock
TriggerDel a y
ClockDel a y