Posted By
JamesC
on 2016-12-25
11:27:56
|  Re: PC RS232 Mouse project for Plus/4 User port_a cheap and working one :-)
Just for clarification -- have you built a RS232 interface, or are you suggesting how others might build one (and program for it)?
The Plussy has the 6551, which can do up to 19,400 bps. Does your project utilize it? If we can read RS232 data from the 6551 directly (at $FD00-$FD0F) then we might save precious CPU cycles that would otherwise be spent "decoding" (64/128 term: "bit banging") it. Which may free us to use non-zeropage memory and not worry so much about system speed. 
My two cents/pence/fractional Euro: please don't reassign Speech memory for other purposes. While there aren't any 364s in common use, YAPE supports it. YAPE also supports a lightpen and SID cards, so we should allow for the possibility of YAPE supporting an RS232 interface at some point. If I could use a mouse within YAPE *and* retain Speech, I would appreciate it.
If you are willing to use non-zeropage memory, function key memory is rarely utilized to its potential. You could reassign a few bytes ($05DF-$05E6) and the system would never know. 
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