Re: PET user port programming

Hi Didier,

Pages 101 onwards in "The Pet Revealed" look very interesting - thanks for the link.

Regards,

Chris

> On 10 May 2017 at 12:49 didier derny <didier@aida.org> wrote:
> 
> 
> roughly you have a half 6520 on the user port check the 6520 datasheet
> 
> http://archive.6502.org/datasheets/mos_6520.pdf
> 
> you have the timers in the 6522
> http://archive.6502.org/datasheets/mos_6522_preliminary_nov_1977.pdf
> 
> you can also check this book
> https://archive.org/details/The_Pet_Revealed
> 
> 
> 
> On 10/05/2017 12:25, Chris Wareham wrote:
> > Hi,
> >
> > I've just signed up to the list as I'm currently writing a simple MIDI sequencer for my PET 4032. I'm using the cc65 compiler suite, but having difficulties finding information on user port programming and timing.
> >
> > At the moment I have a home made circuit on a breadboard with an LED for each of the data pins on the user port. When I write a byte to the data register for port A the corresponding LEDs light up. The missing pieces of the jigsaw are how to do the timing so that bytes get written at the correct intervals and the handshaking so I know when each byte has been read. I'm guessing I do the timing by setting a timer and handling interrupts, but neither of my two PET programming books cover this.
> >
> > MIDI messages consist of three bytes, but I've got my pseudo MIDI messages down to two bytes:
> >
> > mnnnnnnn ccccvvvv
> >
> > Where:
> >
> > m is 1 for note on or 0 for note off
> > nnnnnnn is the note number 0-127
> > cccc is channel 0-15
> > vvvv is velocity 0-15
> >
> > MIDI supports velocity values of 0-127, so I plan on shifting my 4 bit value to get a reasonable spread of velocities. I plan on using an Arduino to convert my pseudo MIDI messages into real ones. Hopefully I can then make an interface with a suitably programmed Atmega chip rather than a complete Arduino board.
> >
> > Any advice will be most gratefully appreciated!
> >
> > Regards,
> >
> > Chris
> >
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> 
> 
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