Cronologic Ndigo Crate Guide de l'utilisateur télécharger pdf (Page 13)

2.4 Ndigo250M-14 Functionality

The analog input signal is quantized to 14 bits. However, the board always scales and oﬀsets

the data to 16 bit signed data centered around 0.

Interleaving of multiple channels is not supported

2.4.1 Zero Suppression

One of Ndigo250M’s key features is on-board zero suppression to reduce PCIe bus load. Only

data that passes speciﬁcations predeﬁned by the user is transmitted. This guide refers to the

data structure in which wave form data is transmitted as “packets”. A packet contains the wave

form data and a timestamp giving the absolute time (i.e. the time since start of data acquisition)

of the packet’s last sample.

Figure 2.9 shows a simple example: Data is written to the PC only if values exceed a speciﬁed

threshold. Expanding on that, Ndigo250M’s zero suppression can be used to realize much more

complex scenarios.

Retrigger

Precursor Postcursor

timestamp

Figure 2.9: Simple zero suppression: Only data with values above a threshold are written to the

PC.

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Cronologic Ndigo Crate Guide de l'utilisateur Page 13