Re: SPI etc. ... does writing PortB affect the 9.6kbps serial port?

As I expect people know, there is a serial port interface wiring that
can achieve 9.6kbps on the C64 ... Daniel Dallman's design

http://members.tripod.com/~ilkerf/chard/rs232c96.txt

12.5. in FAQ:

http://faqs.cs.uu.nl/na-dir/commodore/main-faq/part7.html

The 9600 bps uses sp2 and cnt2, so hardware SPI is incompatible. But
an el-cheapo serial flash would be possible using pb2, pb3, pb4, and
pb5, and bit banging. It would still support, for example, a wedge
that downloads and executes a 4K module into the open high ram (and
the default module downloaded could of course be a menu that offers up
other modules for download into the same space), and downloads and
uploads RAM buffers on some simple system ... a call to a routine with
base page in Y, number of pages in X, direction in the carry flag.

However, how that would be done would be dependent on whether using
those bits interacts with the routines that make use of the 9600bps
asynchronous serial interface. If not, the routines can be
independent. If so, the routines have to be written so that they do
not walk over each other.
.