Synchronisation of Function Generators at COSY by kfi28201


									                Synchronisation of Function Generators at COSY
          T.Vashegyi, N.Bongers, B.Dahmen, C.Deliege, D.Gehsing, K.Henn, M.Simon,, H.Zens

Ramp generation at COSY is done by so                MHz clock signal to the function
called function generators, which supply             generators.
the dynamic power supplies with 24 bit               The central clock was realised as a VME-
digital values each s.[1] Once started by

                                                     Board with a highly precise clock-source (
an external trigger of the timing system the         a Rubidium Rival OCXO) , with three
output of these values is clocked at 8 MHz           MAU interface output on the board for
by quartz oscillators located on the                 transmitting the precise clock-source and
generator boards. The precision of these             driving three bus structures at the same
oscillators is fully sufficient for normal           time. This enables a mixed star-bus-
operation but the drift between them                 architecture where the three different
prevents special investigations at the end           Cheapernet-like       coaxial     buses    are
of long ramps, for example polarisation              connected to one clock source. The number
measurements. To overcome this limitation            of coaxial buses is expandable - always by
a new synchronisation hardware is                    three buses - using more VME-boards in
designed for the synchronous operation of            the same VME central clock crate. The
the function generators and other                    MAU interfaces of the VME-boards are
components of the control system at                  supplied by the same one OCXO clock-
COSY. Based on the distribution of a                 device source. The same type of VME-
central clock, the synchronisation together          board can be used to connect a target
with the timing system will guarantee a              VME-crate to a coaxial bus via an MAU
highly synchronous operation of the                  interface input for receiving the central
connected components. The simple way of              clock-signal and driving a spare VME-bus
the distribution of the central clock enables        signal . Little hardware modifications have
the use of this continuous clock as a                to be done for all those function-generator
general clock on the whole area of the               boards which have to be synchronised with
accelerator, not only for control                    the central clock, i.e. the local clock has to
components but for experiments and other             be replaced by the 8MHz clock signal from
hardware components too. .                           the back-panel (VME-bus P2-connector ).
The hardware components, are connected               To synchronise other fast VME-CPU- and
via a 10BASE-2 (Cheapernet) local area               VME-DSP-boards with the central clock
network, using a 50 Ohm coaxial cable and            in target crates - even with more 100MHz -
Media Attachment Units (MAU) at each                 the      above       mentioned       hardware
node as the physical layer and the timing            modifications have to be done combined
system uses a separated, distinguished               with the replacement of the fast VME-
network with the same hardware. This                 board local oscillator by a PLL-clock-
kind of coaxial physical layer with its              multiplier which one as an input the central
simple bus structure, T-connections and              clock from the target VME-bus uses.
isolated MAUs is working very reliable in
our accelerator environment with a data              References:
rate of 10 Mbit/sec. The idea was to use             [1] K.Henn et. al. “Function Generation and
                                                     Automatic Resynchronisation for the Dynamic
this hardware to distribute a continuous 8           Components of COSY”, IKP Annual Report 1993

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