21
CS269: HW/SW Engineering of Embedded Systems, Winter02
Processes and Media
process P1{
  port reader pX, pY;
  port writer pZ;
  thread(){
   while(true){
      ...
      z = f(pX.read(), pY.read());
      pZ.write(z);
    ...
    }
 }
}
medium M implements reader, writer {
   word storage;
   int n, space;
   void write(word z){ ... }
   word read(){ ... }
}
P2
M
P1
pY
pX
pZ
Interaction among processes is made through media:
interface reader {
    update word read();
    eval int n();
}
interface writer {
    update void write(word x);
    eval int space();
}
Media may have ports to call methods of other media.