ADLINK Technology MCM-100, User Manual

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38 Operation
Leading
EDGE COMPUTING
4.1.4 Data Transfer
Software Polling Data Transfer (Non-Buffering Pro-
grammed I/O)
Polling mode supports flexible timing and is suitable for retrieving
recent data without FIFO buffering latency. The MCM-100/102
continuously updates the most recently acquired data onto a data
port for specific channels. Data not retrieved in time is overwritten
with new data without notification. The UD-DASK Function Library
Reference provides corresponding software API details.
Continuous Acquisition Mode
Differs from software polling mode only in the generation of block
data in continuous acquisition mode without the need to consider
data overwriting or acquiring repeat data in software polling mode.
This mode is suitable for when continuous data is to be acquired in
a fixed and precise time interval. Please note the data buffer size
must be a multiple of 256 in continuous acquisition mode. The UD-
DASK Function Library Reference provides corresponding soft-
ware API details.
4.1.5 Anti-Aliasing Filter and Frequency Response
The filter limits the bandwidth of the signal path and rejects out-of-
band noise. The digital filter of the Sigma-Delta ADC sets the over-
all frequency response, using multi-stage FIR topology to provide
linear phase with minimal passband ripple and high stopband
attenuation. These image frequencies, if present in the signal and
not externally filtered, will fold back (or alias) into the passband,
causing errors. The stopband of the ADC provides 100dB attenua-
tion of frequencies that begin just beyond the passband and con-
tinue out to ADC over-sampling rate. The MCM-100/102 provides
an anti-aliasing, low-pass, simple RC filter in front of the ADC
inputs to limit possible high amplitude out-of-band signals and
noise.