M4i & M4x enhancement details

These enhancements are included with each card purchase to increase the versatility of the M4i & M4x 22xx and 44xx and series of signal capture cards. Please contact DataQuest Solutions should you require any further information.

ABA mode

Diagram showing ABA mode operation

ABA mode this allows changing from long-term slow and continuous data logging (through a process of sample decimation), to ultra-fast acquisition on a trigger event. This is handled by the hardware. This is more efficient than having to write code in a post-process program and helps isolate in detail interesting events from reams of data.

In the above diagram the decimated data capture points are shown as blue lines. When a trigger is applied the data is recorded at the full clock speed, here depicted by the green lines in section B. Data is captured for a user definable numbers of times. Pre and post trigger data can be recorded at the full rate if required so that analysis of the signal leading up to the trigger, as well as that following can be performed.

ABA mode significantly reduces stored file sizes. At the sort of rates these ultra high-speed cards can operate, this is a big advantage. The level of decimation can be set in the driver code or the SBench software. The trigger point can be external an TTL pulse, or from the amplitude of the analogue input signal.

Multiple Recording

Image showing signal data transfer following rapidly repeating triggers

Multiple Recording allows the capture of signal data associated with every one of many trigger events, without having to restart the hardware. Trigger events which repeat at a very high rate could thus be recognised with this option without risk of any being missed. A trigger re-arm period is required immediately after each capture event, however for the M4i & M4x.44xx series of boards this is just 40 samples (+ any pre-trigger samples) in length. For the ultra-fast 22xx range, then it is between 80 and 320 samples depending on the card model. More information is given on the card datasheets. Should the user intentionally wish for an extended delay between trigger arrival and each recording this is software programmable too.

The memory of the board will be divided into several segments of the same size. Each segment will be filled with data (or played from) when a trigger event occurs.

When using boards of the M4i.xxxx series, Multiple Recording/Replay may be combined with the Time stamp option to very usefully record the start time of a segment.

Gated Sampling

Gated sampling. Signal data transfer period controlled trigger signals period

The option Gated Sampling allows recording of a signal controlled by an external gate signal. Data is only recorded if the external gate signal is equal to a programmed level (TTL HIGH or TTL LOW). As with the Multiple-Recording option (see above) a delay of a few samples between trigger and recording occurs, but again easily compensated for by pre-trigger samples.

As an option to all M4i signal capture boards, the start and end sample of a gate interval may be marked in memory by combining with the Time stamp option to record start and end of a gate interval.

Time Stamp

Image showing each successive time stamp relative to triggers The time stamp function allows recording of trigger moments relative to the start of recording or synchronised to an external radio clock. The time stamp function is designed as an enhancement to the Multiple Recording and the Gated Sampling mode but could also be used without any of these options. The memory of the time stamp function is a FIFO buffer and this allows continuous signal recording with time stamps. Each time stamp is defined by samples and therefore the rate of the A/D converter clock. The relationship between trigger events and the count are set by the modes as described below.

Standard Mode

In standard mode the time stamp counter is set to zero once, with a call to TS_RESET. After this call the counter counts continuously. The time stamp of all recorded trigger events are referenced on this common zero time. With this mode the exact time difference between different recordings may be calculated.

StartReset Mode

In the StartReset mode a time stamp value calculated from a counter value which increments automatically from zero after the initial start of the card, each trigger that comes along is then time stamped. In Multiple Record mode (described above) many such trigger events can be very close together to capture many individual segments of data in a recording. StartRest mode is very useful here as each segment is individually time stamped. The counter only zeros after the end of the complete recording and the restart of the card.

In addition, if this time stamping is used with Gated Sampling instead, a time stamp will show the start and also the end of the gate.

RefClock Mode

The counter is divided in a HIGH and a LOW part. The HIGH part counts the seconds that have elapse since reset of the whole counter and references the seconds signal of an external radio clock, or any user precise 1Hz signal which is fed into the multi-purpose digital inputs easily accessible on the end plate of the card. The LOW part is reset every second, and defines the position of the trigger event within the current second. This mode allows the absolute time of a trigger event to be recorded.

Note: The HIGH counter part need not be used for counting seconds, it could be used to simply extend the count range for recording the external triggers, this is what happens in Standard and RefClock modes.

DataQuest Solutions Ltd. | Phone: 01526 557171 | Email: info@dqsolutions.co.uk