10.1 Sampling Modes

There are several different A/D sampling modes available on Diamond-MM-32DX-AT. The mode in use is selected with the FIFO enable and Scan enable bits at the FIFO control register at Base + 7 as well as the A/D interrupt enable bit in the Interrupt control register at Base + 9.

Note that the FIFO should not be enabled if interrupts are not enabled, as the FIFO storage is only useful when interrupts are being used and will have no effect otherwise. All these features may be selected as arguments to function calls in the driver software.

The control register details are provided for completeness and for programmers not using the driver

Scan	FIFO	Interrupt	Mode	Description
No	No	No	Single conversions	The most basic sampling method. Used for lowspeed sampling (typically up to about 100Hz) under software control where a precise rate is not required, or under external control where the rate is slow. Consists of either one channel or multiple channels sampled one at a time.
Yes	No	No	Scan conversions	Used to sample a group of consecutively numbered channels in rapid succession, under software or external control. The time between samples in a scan is programmable between 5 to 20 microseconds, while the time between scans depends on the software or external trigger and may be very short or very long, but is usually less than about 100Hz (above this rate use interrupt scans below).
No	No	Yes	Interrupt single conversions, low speed	Used for controlled-rate sampling of single channels or multiple channels in round-robin fashion, where the frequency of sampling must be precise but is relatively slow (less than 100Hz). The sampling clock comes from the on-board counter/timer or from an external signal. The interval between all A/D samples is identical.
Yes	No	Yes	Interrupt scans, low speed	Used for controlled-rate sampling a group of channels in low-speed mode (less than 500Hz per channel). Each sampling event consists of a group of channels sampled in rapid succession. The time between scans is determined by the sample rate
No	Yes	Yes	Interrupt single conversions, how speed	Intended for medium- to high-speed operation (recommended above about 500Hz). Can support sampling rates up to the board’s maximum of 250,000Hz. May also be used at slower rates if desired. The sampling clock comes from the onboard counter/timer or from an external signal.
Yes	Yes	Yes	Interrupt scan conversions	Used for high-speed sampling of a group of channels where the scan rate is high. The sampling clock comes from the on-board counter/timer or from an external signal.