Sequence Replay Mode

The sequence replay mode is a special firmware mode that allows to program an output sequence by defining one or more sequences each associated with a certain memory pattern. Therefore the user is provided with two different memories, one for the sequence steps and one for the data patterns. The separated sequence memory can hold different sequence steps (the actual number depends on the hardware and can be found in the technical data section). Each step itself contains information about how often it should be repeated in a loop, which step will be next and on what condition the change will happen. To define the pattern for the steps, the on-board memory is split up into several segments of different length. The switch over from one segment to the other is seamless, without any missing samples or spikes. The powerful sequence mode option adds a huge variety of different application areas to Spectrum’s generator cards.

Data Segments in Memory

The complete installed on-board memory of the card is divided into a user de finable number of segments. Each segment space has the same length limiting the maximum length of one data segment to [Installed Memory] / [Number of  Segments]. Each data segment can be filled by the user with patterns of different lengths or can even be left completely empty if unused. In our example we see the complete installed card memory is being split into 8 segments and 6 of these segments are actually filled with data sequences of different length afterwards (indicated in red). Two of these segments are not needed for the assumed sequence and therefore left empty as an example. Due to the fact that each sequence step can be associated with any of the data segments, it is also possible to use one data segment in multiple steps or to just once upload the data for multiple sequences, and just change 
the order of the sequence.

Steps in Sequence Memory

The sequence memory defines a number of data loop steps that are executed step by step either linear or interrupted by waiting for trigger event. The first step that is entered after a card start is separately defined by software. When being entered, each step first repeats the associated data segment the number times defined by its loop parameter. Afterwards the sequencer will either automatically proceed either unconditionally or check for a trigger event as a condition to change over to the next step, which is defined by the steps next parameter. This next segment can be the same segment again performing an endless loop or the beginning of the sequence to repeat the sequence until being stopped by the user. Additionally a step can also be defined to be the last step in a sequence such that the card is stopped afterwards. 

Sequence Restart Mode

The sequence restart mode allows to run any sequence consisting of multiple segments with loops multiple times upon receiving a trigger event. The trigger-to-output time is fixed and doesn't change on any of the runs. Data only needs to be uploaded once and the sequence restart mode runs independently for hours or days if needed. This mode allows to setup long and complicated sequences that are for example used to control some external hardware in a precisely defined way without the need to calculate long data streams and upload data for seconds. Even a change of the sequence or the data doesn't need much time: Simply disable the trigger, execute your updates to the sequence or the segment data and enable the trigger again.

Changing Sequences during Runtime

Due to the strict separation of the two memory areas it is also possible to change the sequence memory during runtime. Any of the three step parameters „Next“, „Segment“ and „Loop“ of any step in the sequence memory can be changed during runtime, without  corruption the sequence memory. However once a step is entered, it will first execute the current parameters such as replay the associated pattern and repeating it the programmed number of times.

In addition to the possible runtime changes within the sequence memory as described above, it is also possible to change the parts of the pattern memory. However since the data memory’s nature is not „read-before-write“, the user must take care not to change the content of the memory segments, which are used within the currently active sequence. Changing the data pattern can be useful in applications, where the data for the next test needs to be updated based on results from the 
currently running test. Remember to update the sequence step entries if the segment length has changed, so that the driver can automatically 
re-calculate the internal start-addresses of the segments.

Supported AWGs and Digital Generator Products

The following products from Spectrum support the Sequence Replay Mode as a standard feature. Please note that the Sequence Restart feature was added at a later stage and requires the latest driver to be used:

• 65xx series - low speed AWGs from 40 MS/s to 125 MS/s: 65xx Series
• 66xx series - mid speed AWGs from 625 MS/s to 1.25 GS/s: 66xx Series
• 75xx series - low speed Digital I/O card with 125 MS/s: 75xx Series