RE: CIA Serial Registers on C128
Date: 2002-02-27 08:18:59

Hello Ruud,

>> If I connected the interface to the userport and used all 
>> four signals I intend to, will the internal circuitry
>> disconnect activity on CNT1/SP1 from the userport so that
>> burstmode continues to work without having to
>> physically unplug the device?

>I have some troubles understanding your question.

You understood my question perfectly.

>If you take care that your device tristates these lines when not in
>operation, theoretically everything should be fine regarding the C128 using
>the IEC-bus.

>On the other hand nothing may pull DATA and SQRIN Low otherwise CNT1 or SP1
>could be blocked.

I've since checked the circuit (not just read text descriptions...) and you
are correct. I was thinking to simply use a DIODE and have the device drive
the line high when not needed. I can never remember which way to face the
DIODE, but do you think that this will be enough to avoid pulling on CNT1
and SP1?

Regards, Nick 


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