On 25.09.2018 20:42, cbmeeks wrote:   
   > I'm curious about how to access certain pins of the C64 User Port.  Going by   
   the pinout here:   
   >   
   > https://www.c64-wiki.com/wiki/User_Port   
   >   
   > I see there are some pins I'm not familiar with.   
   >   
   >   
   > 4       CNT1	Counter 1, from CIA #1   
   > 5	SP1	Serial Port 1, from CIA #1   
   > 6	CNT2	Counter 2, from CIA #2   
   > 7	SP2	Serial port 2, from CIA #2   
   These come from appropriate pins from appropriate CIA chips. You can use   
   these for fast serial connections. The clock comes from cnt pin and data   
   from sp1. Or if you input something, the chip reads from sp1 when clock   
   signal comes.   
      
   > 8	/PC2	Handshaking line, from CIA #2   
      
   I do not exactly know about this.   
      
   > 9	ATN	Serial attention in   
      
   I do not know why this is here. It is the same signal as in serial port.   
   Could it be that CBM thought that serial ports could be used with fast   
   drives?   
      
   > ...   
   > B	/FLAG2	Flag 2   
      
   A handshake line. This can be tied to a interrupt.   
   > ...   
   > M	PA2	PA2   
      
   You can use this pin as PB0-7. It has a DDR register and you can use it   
   as input or output. Usually used as handshake line.   
   >   
   >   
   > I have a basic idea what the counters are for but I'm looking for more   
   detailed information on all of those pins.   
   >   
   > Are there any programming and/or schematics out there that indicate how to   
   use them in various projects?   
   >   
   > Thanks   
   >   
      
   --- SoupGate-Win32 v1.05   
    * Origin: Agency HUB, Dunedin - New Zealand | Fido<>Usenet Gateway (3:770/3)