INTL 3:770/1 3:770/3   
   REPLYADDR jl@650pot.com   
   REPLYTO 3:770/3.0 UUCP   
   MSGID:  2c176ae1   
   PID: SoupGate-Win32 v1.05   
   XPost: sci.electronics.design   
      
   Something I've wondered about:   
      
   Suppose we have a c program running on some little uP, and it has some   
   integer variable value, 8 or 12 bits or something, and wants to drive   
   a parallel DAC off-chip.   
      
   The msb...lsb bits of the variable obviously have to get to the right   
   pins of the DAC.   
      
   So, in general, how does one pick the physical i/o port pins on the   
   uP, to get the order right? The PCB layout is easiest if we just wire   
   the DAC to the handiest port pins.   
      
   One could test and bit-bang each bit and port individually, and then   
   strobe the DAC, but that's inelegant.   
      
   In the RP2040 chip, one can apparently write to a register in a   
   PIO/state machine block, where each bit of the register can be   
   assigned to drive a physical port pin. I think there are some   
   constraints on the selected pins.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: Agency HUB, Dunedin - New Zealand | Fido<>Usenet Gateway (3:770/3)   
   SEEN-BY: 10/0 1 90/1 103/705 105/81 106/201 124/5016 129/305 153/757   
   SEEN-BY: 153/7715 218/0 1 601 700 840 870 930 220/70 221/1 6 360 226/17   
   SEEN-BY: 226/30 100 227/114 229/110 111 114 200 206 300 317 400 426   
   SEEN-BY: 229/428 470 550 616 664 700 240/1120 266/512 267/800 282/1038   
   SEEN-BY: 291/111 292/854 301/1 113 812 310/31 320/219 322/757 335/364   
   SEEN-BY: 341/66 342/200 396/45 460/58 633/280 712/848 770/1 3 100   
   SEEN-BY: 770/330 340 772/210 220 230 5020/400 1042 5058/104 5075/35   
   PATH: 770/3 1 218/840 221/6 301/1 218/700 229/426