M200 interfacing

From: Sellam Ismail <foo_at_siconic.com>
Date: Sun Dec 29 12:49:00 2002

On 29 Dec 2002, Frank McConnell wrote:

> Except that, if you want to read binary cards (trust me, you will --
> those binary cards are contain boot and other code for these
> machines), you need to do all 12 rows. 80 columns x 12 rows = 960
> bits / 8 bits per byte = 120 bytes per record.

One step at a time. Right now I'm focused on getting the character data
off the cards I have (mostly FORTRAN programs and numerical data).

> You've got RAM in the Apple, use it as a buffer between the card
> reader and the serial port. 16KB would hold 136 full card images,
> which you might think would be more than enough time to tell the
> reader to stop picking cards and actually have it stop. So, when the
> buffer's fullness gets above some threshold, stop picking cards until
> it gets below some lower threshold.

If the data can't be transmitted between card picks then it can be
buffered and, when it reaches a certain threshold, the pick signal can be
de-asserted until the buffer clears the threshold, then picking can

> You may be able to do some cheap buffer- and serial-time savings by
> either run-length encoding or just keeping a record length and not
> storing or sending trailing blank (unpunched) columns. Depends on
> your data. I think I would go for this last.

Hmm, good idea. I hadn't considered that. It would certainly make no
sense to buffer or transmit trailing blanks.

Sellam Ismail Vintage Computer Festival
International Man of Intrigue and Danger http://www.vintage.org

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Received on Sun Dec 29 2002 - 12:49:00 GMT

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