Mixed-Mode digital add-on for the Spectrum M2p.59xx-x4 digitiser cards


Digital add-on, here shown both with SMB and FX2 connection options on extra slot plate.

Using an optional module for the M2p.59xx-x4 range of digitiser cards, 16 LVTTL digital multi-purpose I/O lines can be added. The additional digital lines add to the four multi-purpose "XIO" lines that are already standard on the digitiser connector panel. A total of 19 asynchronous (polled) digital inputs are now be possible, or 20 asynchronous outputs. The synchronous inputs are one less in number as one multi-purpose line is for output only. Set all the lines to be inputs and these can operate synchronously to the analogue inputs.

The synchronous digital data is stored inside the analogue samples by reducing the resolution. So for example, if using an M2p digitiser with 8 analogue channels and the requirement is to store 8 bits of digital data, each analogue channel can be programmed to hold one bit of digital data, reducing the analogue channel resolution to 15 bits. It is also possible to completely use one 16 bit analogue channel to hold 16 bits of digital data.

If your requirement is to capture (with every detected trigger event) a block of analogue samples, repeating this multiple times, then the digital data can instead be stored with each trigger timestamp at the end of each user defined sample block length. This way no analogue channel resolution is reduced. Note that in this case, the status of the digital lines is only captured at the time of the trigger event, not every sample.

Physically the digital option is a piggy-back module on the digitiser card. For wiring connection it comes in two different versions, one with SMB connectors the other with a FX2 flat-ribbon connector. The SMB-version (M2p.xxxx-DigSMB), shown here on the left of the image, offers ten connectors on the front panel of a second computer PCIe slot bracket space. Six more are available internally. The latter can be used for PC-internal cross connection or via external connection via a third slot bracket. The FX2-version (M2p.xxxx-DigFX2) guarantees compatibility with predecessor products from Spectrum and allows parallel connection of all lines through a single connector.

There is much versatility in setting up the capture of analogue and digital data in the mixed-mode operation, beyond that described above. See the M2p.59xx-x4 datasheet for a listing of functionality. The software drivers allow customised setups that can generate perfectly matching mixed-mode solutions.



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