[Coco] *SLENB behavior?

Mark J. Blair nf6x at nf6x.net
Thu Nov 10 10:29:30 EST 2016

> On Nov 9, 2016, at 23:24, Darren A <mechacoco at gmail.com> wrote:
> Cartridges which use the SLENB* signal should do so in a Wired-OR fashion
> (an open-collector or open-drain output).  You should do the same for the
> CART* and NMI* interrupt lines as well.

Program Paks simply connected CART* to Q, and the Multi-Pak MUXed the CART* signals from each slot. The MPI also provided a 4.7k pull-up for each slot's CART* signal. Either a totem-pole or wired-or driver should be fine for CART*.

NMI*, HALT* and SLENB* should be treated as wired-or signals, though, even if some contemporary designs got that wrong.

Mark J. Blair, NF6X <nf6x at nf6x.net>

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