The first version of this cassette tape interface can either run off the SID and SOD lines on the SBC-85 backplane or it can use an I/O port header.  On most systems the SID/SOD are probably busy with the RS232 interface on the SBC board and the expansion port is inconvenient because it takes one bit out of two different ports (unless running off a 8755 with its bit defined port direction)

So I am thinking that v2 will be stand alone and take its own I/O space.  I have not decided if this should be via an I/O chip like the 8255 PPI so there are additional ports available or if I should just create one port for the cassette interface and have this card dedicated just to the cassette.  No more work either way, but the 8255 is a little harder to find for most than just a 74xx latch.

I have a few other things on the front burner now and it will be a month or so before I am submitting another board run so time to think about it.  Any suggestions would be appreciated.