Waveform Start Modes -
The DST501 has four different waveform start modes:
- Restart
- Master
- Slave
- Auto Trigger
The four modes differ in the way the module generates waveforms. In Restart mode, the module generates waveforms by user command in the GUI. For Master mode, waveforms are generated by an external signal to the TRIG connector. For Slave mode, waveforms are generated by an external signal, usually from another module, to the SYNCIN connector. Finally, in Auto Trigger mode, the module generates waveforms from a periodic signal that is produced by the onboard FPGA.
Waveform Start Features
Internal START Signal
The module now uses an internal START signal to generate waveforms. In Restart
mode, the START signal is activated when the user sends a signal from the GUI.
In Master mode, the START signal is activated when the module senses a rising
edge from the TRIG connector while armed. In Slave mode, the START signal is
activated when the module senses a rising edge from the SYNCIN connector while armed. In
Auto Trigger mode, the START signal is activated when the module senses a
rising edge from an internal clock supplied by the module.
Guard Page
This feature is used to provide phase accuracy when generating waveforms in Burst mode only.
The Guard page is essentially a null memory page used before the waveform to output the exact
phase that the user wants. In the DSM, the null memory page will output a phase of 0. If phase
accuracy is not important to you then you do not need to use the Guard page since it adds latency
to the trigger signal to beginning of waveform generation time. If you do use the Guard page, you
would need to specify the Guard Length which the length of the guard page in data points.
Usually we recommend a Guard Length of "128" (decimal).
Restart
In Restart mode, the module generates the START signal when the user clicks on the “Restart” button in the GUI or presses “F3” on the keyboard.
The PC host sends the command through the USB to the module. Therefore, there will be an uncertain delay due to the USB traffic, which can be on the order of a few hundred microseconds.
The Restart mode can be used in conjunction with the Auto Trigger mode and with either the Master mode or the Slave mode.
The figure below illustrates the Restart mode inputs and outputs.
Master
In this mode, waveforms will start when the board senses a rising edge from the TRIG connector while armed. The module must first be set to armed by clicking on the “Arm” button in the GUI or by pressing “F2”. If the board is not armed then the signal from the TRIG connector will be ignored.
When armed, the signal from the TRIG connector will cause the START signal to go high, which will then generate waveform output.
In Master mode, the module will output a pulse through the SYNCOUT connector for each rising edge it senses from the TRIG connector. The SYNCOUT signal can then be used to trigger a Slave board.
The Master mode can be used in conjunction with the Restart mode and with the Auto Trigger mode.
The diagram below illustrates the Master mode inputs and outputs.
Slave
In this mode, a waveform will start when the board senses a rising edge from the SYNCIN connector. The board must first be set to armed by clicking on the “Arm” button in the GUI or by pressing “F2”. If the board is not armed then the signal from the SYNCIN connector will be ignored.
When armed, the signal from the SYNCIN connector will cause the internal START signal to go, which will then start waveform output.
In Slave mode, the module will NOT output a signal through the SYNCOUT connector.
The Slave mode can be used in conjunction with the Restart mode and with the Auto Trigger mode.
The diagram below illustrates the Slave mode inputs and outputs.
Auto-Trigger
In this mode, the user specifies the frequency of a trigger signal without the use of an external signal such as those used in the Master and Slave modes. The trigger signal is internally generated but may not be as accurate as an external trigger. The frequency of the internal trigger signal is specified in the GUI.
If Auto Trigger mode is selected, there will be no SYNCOUT output signal.
The Auto Trigger mode can be used in conjunction with the Restart mode and with either the Master mode or the Slave modes.
The diagram below illustrates the Auto Trigger mode inputs and outputs.
Combining Modes
The four modes do not need to be run separately. The user can run two or three modes at the same time. The following are valid combinations of combining modes:
Restart and Auto Trigger
Restart and Master
Restart and Slave
Auto Trigger and Master
Auto Trigger and Slave
Restart and Auto Trigger and Master
Restart and Auto Trigger and Slave
The only rule to combining modes is that while the module is generating a waveform, it will ignore any other signals that would normally be able to activate the START signal. After completing the waveform, the first signal that the module senses will be able activate the START signal and result in the next waveform generation.
As an example, assume that the module is in Auto Trigger and Master mode and generates the first waveform after sensing the rising edge from the internal trigger. While the module is in the middle of generating the waveform, a rising edge is detected from the TRIG connector. Since the module is busy, this signal will be ignored. When the module has finished generating the waveform, it again senses a rising edge from the TRIG connector. This time, the module will activate the START signal and thus generate the next waveform.
