5/7/99
                                                        B.Baldin
                                                        D.Wood
                                                        

      Requirements for RS-232 interface with muon front-end units
      ===========================================================

1. Muon  front-end units  include PDT  Control Board  (CB), Scintillator
   Readout Controller (SRC),  Mini-Drift tube Readout Controller (MDRC),
   SC and MDT VME processors. Comminucations with the listed above units
   via  RS-232  interface  has to be   implemented in  the  software and
   hardware  in a uniform  way to  ensure simple  remote  operations and
   intersystem compatibility.

2. The following are mandatory requirements for implementation RS-232
   based communication links for muon front-end units:

    - ASCII data encoding 

    - 9600 bps default communcation speed (i)
 
    - software or hardware handshake (user defined) (ii)

    - standard  shielded cable  connection  to the  terminal port server
      with one RJ-45 and one DB-25 connector at the ends (iii)

3. These  communication links are  implemented as an  auxillary tool for
   debugging and  diagnostic purposes and cannot  be used instead of the
   1553 bus interface,  which is exclusively  used by the D0 CDAQ system
   for monitoring and control. 

Notes:   

      (i)  RS-232  port  connected to  the  MRC has  2.5  Mbit/s default
           communication speed

      (ii) RS-232  port connected to  the MRC uses  synchronous mode and
           handshake

      (iii) a 26 pin 3M to  DB-25 connector  adapter will be used for SC
            VME40 processors