Jurgen Engelfried
                                                 Alessandro Bravar
                                                 November 2, 1994



         Specification for the new RMH to DYC+ Interface for E781
         --------------------------------------------------------


To readout the RMH system in E781, a readout controller/interface has to be
build replacing the standard CAMAC Interface. We will summarize here the
properties that the new module must have, sometimes comparing to the present
CAMAC readout system.

The E781 DAQ is based on DART. This system is interfaced to the CAMAC FERA
system by DYC+, which basically replaces the FERA controller and serves as
a buffer and as a converter to the DART cable. We will use it to connect
the readout from CROS, RMH and CAMAC (via SCC) to the DART cable.

The RMH readout sequence has to be controlled from the Interface itself 
upon a receipt of a trigger level signal (+ some control signals from DYC+).
All outputs have to feed the DYC+. These are in principal FERA signals, with 
a few exceptions. We will append a timing and level diagramm derived from
the CROS to DYC+ Interface.

We should also keep the present CAMAC readout to perform Offspill tests.

Seen from outside, the module should perform the following global functions:

    - receive an readout trigger 
    - issue a busy signal
    - send two 16bit header words
    - readout RMH modules syncronous (like CROS) or asyncronous (using the
         ACK from DYC+) after the readout trigger
    - clear RMH modules
    - take busy away

To resolve system problems, also an "Abort Readout" signal, which stops and 
resets the system, should be accepted.

Instead of setting a "busy" level, the module could also issue an "RMH Ready"
puls at the end of the readout cycle. In any case, the "busy" time should
include the clear time.

For the header words:  We need 2 16bit words since all the data are packed into
32bit words.  These 2 words can be identical.  The bits for the header word
should be selectable. Switches to be set with a scredriver are sufficient.

Readout the RMH:  The module has to supply all control signals needed internaly
to RMH to perform a readout and give the data to the DYC+ with a 
data ready signal. The system will work at a speed of 200nsec/hit.