On Sun, 29 Aug 2021 at 11:05, Mark Cave-Ayland
<mark.cave-ayl...@ilande.co.uk> wrote:
>
> Here is another small set of ESCC fixes from my attempts to boot MacOS on the
> q800
> machine.
>
> When MacOS loads the OpenTransport extension on boot it attempts to enable
> SDLC mode on the ESCC. QEMU's emulation doesn't support SDLC mode, but without
> these fixes the active low STATUS_SYNC bit in R_STATUS is continually
> asserted causing the extension to hang on startup as it believe it is
> constantly
> receiving LocalTalk responses during its initial negotiation phase.
The ESCC data sheet is the first one I've ever encountered that includes
a multiple-choice test on features of the device ("ESCC Questions and Answers"
on pages 385/386: http://www.zilog.com/docs/serial/scc_escc_um.pdf ) :-)
-- PMM
