[comp.sys.apple2] ADB connects

benson@vuse.vanderbilt.edu (Paul Benson) (06/27/91)

In article <4778.apple.a2.net@pro-nbs> asong@pro-nbs.cts.com (Andi Song) writes:
>In-Reply-To: message from benson@vuse.vanderbilt.edu
>
>        Re: Two mice...
>
>        I think you can. In stores I have seen a Mac with an ADB keyboard,
>then a Kensington TurboMouse, then the Apple Mouse, and they all work fine.
>----

  Umm, I think you misunderstood me.  I know you can do this because that is
  _my_ setup, i.e. keybd, Turbomouse, apple mouse.  And this is on a GS.  No
  real problems, for about 4 years.  Kind of confusing when the mouse lock
  is on & I don't realize it. 
  Anyway, I'll repeat for anyone who did not catch it the first time.  You
  may have upto 11 devices on the ADB port.  BUT to fully utilize it 1 must
  be a keybd, one must be a mouse, & one must be a graphic tablet.  The
  remaining 8 may be any combo of the above.  In my last post I was unsure
  about the ADB y-connector, but since the devices are not screening each
  other for collisions and it is basically just straight wire connections
  then it should work fine.
-- 
  Paul 'BaJa' Benson
  Vanderbilt University
  GEnie: P.Benson1     Net: benson@vuse.vanderbilt.edu

David.Empson@actrix.gen.nz (David Empson) (06/28/91)

In article <1991Jun27.015258.29179@vuse.vanderbilt.edu> benson@vuse.vanderbilt.edu (Paul Benson) writes:
>   ...  In my last post I was unsure
>   about the ADB y-connector, but since the devices are not screening each
>   other for collisions and it is basically just straight wire connections
>   then it should work fine.

ADB is an open-collector bus.  You can probably have any cable
configuration you like, provided there are no loops in it and the
maximum length isn't exceeded.  There is no problem with Y junctions.

The main limits (from the IIgs Hardware Reference):

Maximum cable length 5 metres, maximum power drain 500 mA (5V).  Cable
capacitance should not exceed 100 pF per metre.

By the way: ADB devices are connected in PARALLEL.  The apparent
serial connections are an illusion.
-- 

David.Empson@bbs.actrix.gen.nz