ADLINK cPCI-9116 - Manual (Page 48)

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• Operation Theory
Note:
1. The maximum A/D sampling rate is 250kHz. Therefore, SI2_counter can’t
be smaller than 96 while using the internal Timebase.
2. The SI_counter is a 24-bit counter and the SI2_counter is a 16-bit counter.
Therefore, the maximum scan interval while using the internal Timebase =
2
24
/24M s = 0.699s, and the maximum sampling interval between 2
channels while using the internal Timebase = 2
16
/24M s = 2.73ms.
3. The scan interval can’t be smaller than the product of the data sampling
interval and the DIV_counter value. The relationship can be represented
as: SI_counter>=SI2_counter*DIV_counter.
Scan with SSH
You can send the SSH_OUT signal on pin 47 of J1 to an external S&H circuits
to sample and hold all signals if you want to simultaneously sample all
channels in a scan, as illustrated in fig 9.
Note: The ‘SSH_OUT’ signal is sent to external S&H circuits to hold the analog
signal. Users must implement external S&H circuits on their own to
carry out the S&H function. There are no on-board S&H circuits.
5.1.3.2 Specifying Channels, Gains, and input configurations in the
Channel Gain Queue
Like software polling acquisition mode, the channel, gain, and input
configurations (single-end, differential, and U_CMMD) must also be specified
in the hardware Channel Gain Queue under scan acquisition mode. Please
refer to 5.1.2.1 for details. Note that in scan acquisition mode, the number of
entries in the Channel Gain Queue is normally equivalent to the value of
DIV_counter (that is, the numbers of samples per scan).
Example:
Set
SI2_counter = 240
SI_counter = 960
SC_counter = 3
DIV_counter = 4
Timebase = Internal clock source
Channel entries in the Channel Gain Queue: ch1, ch2, ch0, ch2