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CITY synchronisation device

The CITY is an ESRF device that aims at providing synchronization features with White Rabbit and RF clock reference.

  • WR: White Rabbit
  • RF: Radio Frequency
  • CITY: CarrIer for applicaTion based on RF over WR sYnchronization
  • PTP: Precision Time Protocol
  • RFoWR: RF over White Rabbit

The goal is to allow very accurate synchronisation of experiments with beam pulses.

It will replace BCDU8 / N354 / Whist modules.


The CITY is a 1U module that provides 16 generic digital stages. There are 12 outputs and 4 Inputs.

These 12 generic digital IO are dedicated to timing and synchronization:

  • Outputs: Pulses and Clocks related to RF clock and Bunch Injection / Extraction sequence or network events.
  • Inputs: timestamps, events distribution, gating on generic outputs, or user-defined application.

I/Os can be extended by 2 commercial or custom LPC FMC mezzanines.

FMC slots are dedicated to user application extension which design is fully user-defined (empty by default).


Interface to the instrument within a control system. The interface is a TCP/IP socket implementing the DEEP protocol specific to DAnCE platform. The controller implements commands and queries which access the control registers.

White Rabbit

White Rabbit (WR) is an extension of Ethernet. It provides reliable deterministic data transfer and sub nanosecond accuracy time synchronization. More details can be found in the dedicated Open Hardware page:

The instrument is connected to the WR network through a SFP connector and an optical fiber. It is connected on a WR switch (WRS) which is a main component of the WR network.

The goal of this mode is to have a common notion of time and frequency with sub-nanosecond accuracy. Receiving / broadcasting control messages all over the network.

Radio Frequence over White Rabbit

This functionality allows reconstructing a RF reference signal in phase on every node connected to the WR network. It is based on a Distributed Direct Digital Synthesis (D3S). More details can be found on the dedicated Open Hardware page:

The CITY instrument shall be configurable and runnable as:

  • Master mode,
  • Slave mode.

RF frequency synthesis & reconstruction parameters:

  • Frequency: up to 500MHz,
  • Phase noise: < 10ps (ideal target < 1.8ps)


Functional block diagram of the CITY City

A brief diagram explaining how the CITY is used:



Minimal configuration example:

address: tcp://lid421:8909   # RPC server address