M200 interfacing continues...

From: Dwight K. Elvey <dwightk.elvey_at_amd.com>
Date: Thu Jan 2 15:17:00 2003

>From: "Sellam Ismail" <foo_at_siconic.com>
>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
>> > 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.

 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.

>Sellam Ismail Vintage Computer
>International Man of Intrigue and Danger                
> * Old computing resources for business and academia at www.VintageTech.com 
Received on Thu Jan 02 2003 - 15:17:00 GMT

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