Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!usc!apple!oliveb!tymix!tardis!jms
From: jms@tardis.Tymnet.COM (Joe Smith)
Newsgroups: comp.sys.amiga
Subject: Re: Ghosting on A1000 keyboard
Summary: It happens
Keywords: keyboard, ghosting, (not broke)
Message-ID: <907@tardis.Tymnet.COM>
Date: 14 Jan 90 09:07:54 GMT
References: <1990Jan6.065639.23629@ccu.umanitoba.ca>
Reply-To: jms@tardis.Tymnet.COM (Joe Smith)
Organization: BT Tymnet, San Jose, CA
Lines: 38

In article <1990Jan6.065639.23629@ccu.umanitoba.ca> umsmigie@ccu.umanitoba.ca (Jason Smigiel) writes:
>	I seem to have a problem with my keyboard, (on an Amiga 1000) If ever
>I have three keys pressed at the same time  I get extra characters typed
>the most common is the sequence 'del' (it's only most common because I use
>'del a lot in delete) When ever I type 'del' quickly I get 'delo'.  I get
>this extra sequence for about half the 3 key sequnces I make.
>	I know that the Amiga 1000 keyboard is desinged in such a way
>that this ghosting will occur BUT only if more than 10 keys are pressed.

Whoever told you it happens only after 10 keys is wrong.

To quote from the Amiga Hardware Reference Manual, 1989 edition, page 247:
	The Amiga keyboard is a matrix of rows and columns with a key
	switch at each intersection.  Because of this, the keyboard is
	subject to a phenomenon called "phantom keystrokes".  While this
	is generally not a problem for typing, games may require several
	keys be independently held down at once.  By examining the matrix
	you can determine which keys may interfere with each other, and
	which ones are always safe.

	Phantom keystrokes occur when certain combinations of keys are
	pressed simultaneously.  For example, hold the "A" and "S" keys
	simultaneously.  Notice that "A" and "S" are transmitted.  While
	still holding them down, press "Z".  On the original Amiga 1000
	keyboard, both the "Z" and a ghost "X" would be generated.  Starting
	with the Amiga 500, the controller was upgraded to notice simple
	phantom situations like the one above; instead of generating a
	ghost, the controller will hold off sending any character until the
	the matrix was cleared (releasing "A" or "S" would clear the matrix).

You will notice that "D" "E" "L" "O" form the 4 corners of a parallelogram
with the top slanted to the left.  Pressing any 3 keys in this arrangement
produces the 4th.
-- 
Joe Smith (408)922-6220 | SMTP: JMS@F74.TYMNET.COM or jms@gemini.tymnet.com
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