[sebhc] H-89 bus pin out Help

bill malcolm wm65805 at hotmail.com
Tue Mar 14 17:11:54 CST 2006

Thanks for the info :  Do you have exact pin out for the 25 pins.  I have
found some of the information on the H-17 card.
bill .

----- Original Message ----- 
From: "Lee Hart" <leeahart at earthlink.net>
To: <sebhc at sebhc.org>
Sent: Tuesday, March 14, 2006 3:48 PM
Subject: Re: [sebhc] H-89 bus pin out Help

> The H89 CPU board has *3* different pinouts for the six expansion
> sockets.
> The leftmost group of 3 are memory expansion sockets. They were
> originally intended to add ROM cards (Benton Harbor BASIC, etc.); thus
> they don't have a Write line. They have the data bus (D0-D7), part of
> the address bus (A0-A12), 3 decoded chip select lines (RD5,6,7), two
> output bits from the General Purpose port (MEM0, MEM1, intended for bank
> select), and the +5v, +12v, and -12v supplies and ground. Later of
> course, they were used for RAM memory expansion (notably another 16k of
> dynamic RAM to bring the total up to 64k). To do this, they added a
> jumper wire and a 16-pin flat cable to bring in the missing Write, -5v,
> and address lines.
> The rightmost group of 3 are the I/O expansion. The rightmost one is
> unique, and intended for the hard-sector controller. The other two are
> identical. These connectors have the data bus (D0-D7), a few address
> bits (A0-A2), Read, Write, Wait, Clock, Reset, four decoded I/O selects,
> 2 bits from the General Purpose port (I/O#0, I/O#1), 3 interrupt lines,
> and the +5v, +12v, -12v supplies, and ground.
> The hard-sector I/O slot replaces 2 of 4 decoded I/O selects with a 5th
> I/O select, and a write-protect output to write-protect the onboard 2k
> bytes of static RAM (only used for HDOS).
> --
> Ring the bells that still can ring
> Forget the perfect offering
> There is a crack in everything
> That's how the light gets in    --    Leonard Cohen
> --
> Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net
> --
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