Chapter 4
Analog Input
©
National Instruments
4-33
X Series User Manual
Other Timing Requirements
The sample and conversion level timing of MIO X Series devices work
s
u
ch that some clock signals are gated off
u
nless the proper timing
req
u
irements are met. For example, the device ignores both AI Sample
Clock and AI Convert Clock
u
ntil it receives a valid AI Start Trigger signal.
Similarly, the device ignores all AI Convert Clock p
u
lses
u
ntil it recognizes
an AI Sample Clock p
u
lse. Once the device receives the correct n
u
mber of
AI Convert Clock p
u
lses, it ignores s
u
bseq
u
ent AI Convert Clock p
u
lses
u
ntil it receives another AI Sample Clock. However, after the device
recognizes an AI Sample Clock p
u
lse, it ca
u
ses an error if it receives an
AI Sample Clock p
u
lse before the correct n
u
mber of AI Convert Clock
p
u
lses are received.
Fig
u
res 4-18, 4-19, 4-20, and 4-21 show timing seq
u
ences for a
fo
u
r-channel acq
u
isition (
u
sing AI channels 0, 1, 2, and 3) and demonstrate
proper and improper seq
u
encing of AI Sample Clock and AI Convert
Clock.
Figure 4-18.
Scan Overrun Condition; AI Sample Clock Too Fast For Convert Clock
Causes an Error
Figure 4-19.
AI Convert Clock Too Fast For AI Sample Clock;
AI Convert Clock Pulses Are Ignored
AI
Sa
mple Clock
AI Convert Clock
Convert Period
Ch
a
nnel Me
asu
red
1 2
3
0
AI
Sa
mple Clock
AI Convert Clock
Sa
mple #1
Sa
mple #2
Sa
mple #
3
1 2
3
0
1 2
3
0 1
2
3
0
Ch
a
nnel Me
asu
red
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