S5t - 10MHz Sync Trigger


The S5t is a module that generates triggers perfectly synced to the 10 MHz reference of the SPI Rack. It does this by dividing the reference in a microcontroller. The microcontroller clock is replaced by the 10 MHz reference and the internal hardware timers are used to generate a divided output. A local 10 MHz oscillator is also present in the module, it can be connected to the 10 MHz input of the module by a cable inside the cassette. The figure below shows a block diagram of the module. The trigger output is designed to drive a 50Ω load with a 2,5V swing. So far the user I/O option has no functionality, this can be added on request. S5t block diagram The output frequency can be set either by the push button or the USB connector on front of the module. Using the push button the user can choose between 18 presets as indicated by the LEDs on the front. The column of LEDs indicate which frequency is selected, while the top row of three LEDs indicate the multiplication factor of this frequency (x1-x2-x5). Using the USB the user is free to choose the exact frequency within limitations of the microcontroller. The USB emulates a serial port on the PC for easy of communication. Windows and Mac OS X users will need to install drivers from here, this is not necessary for Linux users.

Remote control: currently it is not possible to control this module via the controller module, only via the USB on the front of the module. SPI Rack control can be implemented if the need arises.

Communication Protocol

This section describes the USB communication protocol via a virtual serial port.

Click here to show the protocol...


Parameter Value Units Conditions
Output level 0-2.5 V With a 50 Ohm load
Rise/fall times ns 10% to 90%
Additive Jitter 6.7 ps RMS
Trigger frequency range 0.15 Hz Minimum
5 MHz Maximum


Additive jitter from the S5t: S5i Added Jitter