Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!usc!zaphod.mps.ohio-state.edu!casbah.acns.nwu.edu!squishy
From: squishy@casbah.acns.nwu.edu (Shishin Yamada)
Newsgroups: sci.electronics
Subject: Re: 16-pin 558CP?
Message-ID: <1991Mar12.083628.11466@casbah.acns.nwu.edu>
Date: 12 Mar 91 08:36:28 GMT
References: <1991Mar11.223053.1@csc.fi>
Organization: Northwestern University
Lines: 46

In article <1991Mar11.223053.1@csc.fi> jlahti@csc.fi writes:
>I happen to have an old AST SixPakPlus card, and a joystick.
>My son wants to use that joystick, but AST card needs two chips,
>"16-pin IC (No. 558CP) and a 20-pin IC (No. 74LS244)" according
>the manual.
>I found the last one, but in those electronic stores I tried, 
>they could not help me with 558CP, because the manufacturer
>was not mentioned. I even phoned to local AST representative,
>but they were no better. So: can anyone tell or guess, what 
>does 558CP do and who has done it... 
>Yes, I know: it had been easier to byu totally new joystic adapter
>card...

The 558CP is the Quad version of the ever-popular 555 timer. Also the 74LS244
stands for the folloring:
	74 = TTL Familly of Logic Chips
	LS = Low Power Schottkey Type Logic Familly.
	244 = Octal Buffer (Non-Inverting).
The 558CP and 74LS244 are VERY common parts for any good electronics parts
store. Even Radio Shack should carry these. Popular manufacturers of the
588 are Texas Instruments and Motorola. Both chips should not cost more
than $2 (OK, ridiculous price at Radio Shark).

The 558 is probably used as with a potentiometer in the joystick as an
oscillator. The oscillator is then used to 'count' the position of the
joystick by the oscillators frequency. (I dunno for sure, as I am a Mac
Man. It may even be set up as a one-shot, like the old Apple II).

The 74LS244 is used to interface onto the bus line. It has two enable lines
that connect to eight tri-state buffers. This allows the joystick data to
be written onto the bus only when enabled.

A better question might be, why did these chips fry themselves, and you
should consider that before just plugging in the replacements.

 
=====================================================
Shishin "Squish" Yamada                    |\/\/\/|
 squishy@casbah.acns.nwu.edu  /---------\  |      |
 Northwestern University      | Yo      |  (o)(o) |
 Electrical Engineering       |  Dudes! \  ( <    )
 Class of 1991                \__________\ |___/  |
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  "Life sucks, but Death swallows!"          /    \
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