On Thu, Jul 09, 2015, RETRO Innovations wrote:
> On 7/9/2015 12:33 AM, Eric Christopherson wrote:
> >I notice that when I daisychain my 1581 in the first position and the
> >uIEC in the second, the uIEC still works with the 1581 off -- but only
> >on my actual Commodore. When I have them hooked up to the PC via XA1541,
> >I need to have the 1581 on.
> >Why is this?
> >Unpowered devices drag the bus lines down. But, each powered device (and
> >the 64/128) have pullup resistors. If the XA1541 does not, it might not
> >keep the bus high enough to counteract the pulldown of the unpowered 1581.
Great to know. I've heard of those resistors before but never realized
what they were for.