M200 interfacing continues...

From: Dwight K. Elvey <dwightk.elvey_at_amd.com>
Date: Thu Jan 2 18:27:01 2003

>From: "Sellam Ismail" <foo_at_siconic.com>
>On Thu, 2 Jan 2003, Dwight K. Elvey wrote:
>> >On Thu, 2 Jan 2003, John Lawson wrote:
>> >
>> >> On Thu, 2 Jan 2003, Vintage Computer Festival wrote:
>> >>
>> >> > I've got the PICK CHECK signal from the reader going into CB2. I have
>> a
>> >> > 1K resistor going from CB2 to ground.
>> >> ^^^^^^^^^^^
>> >> Try changing to 5K or even 10K (what I always use for pull ups/downs in
>> >> TTL work. I think you're burying the poor PICK CHECK signal. Actually
>> >> all the resistors oughta be 10K, IMHO.
>> >
>> >I'll certainly try that. But I'm wondering why that should be necessary
>> >when the 6522 data sheet says that particular pin is a TTL level output.
>> Hi
>> I thought you were using the pin as an input. As an input,
>> there is no pullup and a floating pin would not be good.
>The pin is an input, but it's normal state is to be off/false. Therefore,
>John's suggestion to put a pulldown resistor on it seems logical. It
>should be normally off, and the M200 should bring it high when it wants to
>signal the PICK CHECK error.
>I'm trying to troubleshoot a more pressing problem right now: the reader
>is picking 5 cards before the Apple thinks 80 Index Marks (e.g. 80
>characters) have been detected. Either my code is wrong, my code is slow,
>or the Apple is too slow to handle the reader input (in which case this
>was all for naught).

 It sounds like something is wrong. Are you reading with BASIC
or at code level. I would think that assembly code should be able
to keep up, as long as you were not expecting it to transfer to
disk while reading. Does the M200 have any kind of handshake?

>I'm heading off to Radio Shack to take a mental break and to get some
>resistors and to see if they can offer me more than just blank stares.
>Sellam Ismail Vintage Computer Festival
>International Man of Intrigue and Danger http://www.vintage.org
> * Old computing resources for business and academia at www.VintageTech.com *
Received on Thu Jan 02 2003 - 18:27:01 GMT

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