[sebhc] H8 optoisolators - aka: disk transfer program

West, Ronald S. RONALD.S.WEST at saic.com
Sat Jun 19 12:58:05 CDT 2004

I think the Original H8-5 board IO was designed to be compatible with TTY
standards as well as RS232 at the time. They can both accomodate 232
voltages as well as 20ma LV and 60ma HV current loops. Think it was more
their usual thourough design philosophy at work. At the time not much was
running at nearly 10khz.


-----Original Message-----
From: sebhc at sebhc.org
To: sebhc at sebhc.org; sebhc at sebhc.org
Sent: 6/18/2004 8:28 PM
Subject: Re: [sebhc] H8 optoisolators - aka: disk transfer program

I suspected that. It was the cheap alternative... :) You want to talk
cheap though, try doing a serial connection on the original Osborne
computer. If I recollect correctly, they used a quad LM3900
transconductance amplifier for the interface. I developed debugging
software (EM-PAC) to control Applied Microsystem EM series emulators and
remember dealing with Osborne issues.

best regards, Steve

>By the way, did Heath use 1488 and 1489 chips for the RS232 along with
>best regards, Steve

 They only used the optos on the H8-5 without any 1488/89's.
On the H8-4 they used a more traditional interface.

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