National Instruments AT-MIO-16X - Manual (Page 79)

Chapter 3 Theory of Operation
© National Instruments Corporation 3-13 AT-MIO-16X User Manual
Continuous Scanning Data Acquisition Timing
Continuous scanning data acquisition uses the configuration memory
register to automatically sequence from one analog input channel
setting to another during the data acquisition sequence. Continuous
scanning cycles through the configuration memory without any delays
between cycles. Scanning is similar to the single-channel acquisition in
the programming of both the sample-interval counter and the sample
counter. Scanning data acquisition is enabled through a register in the
AT-MIO-16X register set. Figure 3-7 shows the timing for a continuous
scanning data acquisition sequence.
Figure 3-7. Scanning Posttrigger Data Acquisition Timing
In this sequence, the timing is the same as the single-channel
acquisition except for the addition of the channel sequencing and the
generation of the SCANCLK signal. The first sampled channel is
Channel 0, followed in time by Channel 1, and finally Channel 2. After
this, the sequence is repeated. For this example, the sequence consists
of Channels 0, 1, and 2 which are cycled through twice to generate six
values of conversion data. After the six samples have been acquired, the
sample counter terminates the data acquisition sequence.
The SCANCLK signal is generated to indicate when the input signal
can be removed from the conversion channel. This signal is available at
the I/O connector and can be used to control external multiplexers for
higher channel-count applications. The rising edge of SCANCLK
signals when the ADC has acquired the input signal and no longer needs
to have it held available. In the scanning acquisition modes, this signal
pulses for every conversion.
Trigger*
DAQPROG
DAQCMPLT
DAQCLEAR*
Interrupt
0 1 2 0 1 2 0 Channel
SCANCLK
CONVERT