€DH/Graham Toal/Discussion paper/Page |P/
€DF/VLSIC Design Aids Group//Introduction/


€CEThe BBC Micro as a Peripheral


   There has been an increased use in the last year of the BBC Micro
as a peripheral attached to a remote computer such as a Vax or a GEC 4090.

Several terminal emulators have sprung up to simplify the connection of
the BBC to these machines, the emulators including VT100, Tektronix,
and Elbit.  Locally, J. Dion & P. Robinson have produced a reasonably
well packaged terminal program which is enhanced by the capability to
scroll back through memory, to set XON/XOFF options etc...

   One or two people have written packages to allow file transfer from
the BBC Micro to its host and vice-versa.  Typical of these is the
CrossTalk program from the Edinburgh Regional Computing Centre which
hosts ICL, DEC and IBM machines talking to Apples, Pets and BBC Micros.

   I believe that it is time to bring these various ideas together,
and design a consistent interface for the BBC Micro as an intelligent
peripheral, rather than a remote terminal.








Disclaimer:  This paper is a personal view of a field not within
           the scope of responsibility of the author, and is offered
           only for interest and discussion.


€PE 
€DF/VLSIC Design Aids Group//Summary of features/


€CEFacilities

   For readers with more important things to do, the following   
page is a quick summary of the features which I see as desirable
in a 'Terminal' product.

   The rest of the paper will woffle on at more length, but probably
not to any greater depth of perception...

  1) A fancy packaged box (a la ABM)

  2) Ability to emulate any common terminal (B/W)

  3) Low-level drivers to handle handshaking, independent of the
     terminal program being run.
     (This would allow applications programs conversing with the
      host to take advantage of Acorn-supplied line-drivers)
 
  4) A FILING SYSTEM interface to the RS232, when the BBC is
     being used as a micro rather than a terminal. (I.e. locally)

  5) An ENHANCED character terminal which is effectively a screen editor
     which gets its input from the RS232 rather than the keyboard.
     (This will allowing scrolling around previously displayed text,
      AND search/replace, local editing and the ability to pick
      text off the screen and send it back.)

  6) An ENHANCED colour graphics terminal protocol

  7) A low-level driver to convert incoming text to 8-bit binary
     dependant only on the transmission medium in use.
     (Unix filters out <EOT>s, PSS filters out top bits, etc.)

  8) Complete control over the micro from the host when using
     either of the enhanced protocols, probably in the form of
     a remote peek/poke & subroutine call (a la Econet).

  9) Host controlled OSCLI call from within terminal protocols
     (This necessitates finding an unused protocol item in each
      terminal protocol emulated.)
     This allows the host to switch protocols, rather than insisting
     that the user press BREAK or some other 'charmed' key.

  10) Tube compatibility.
      This means in particular not that the Terminal ROM should
      still work when a second processor is fitted, but that full
      advantage should be taken of having two processors.
      (E.g.  That the text buffer (NOT the input buffer which MUST
       be on the IO processor - but the one in which editing may be
       done) is on the 2nd processor, and therefor as large as possible.)