X13.Periphery.TWIDriver.Expander.PinChanged C# (CSharp) Method

      private void PinChanged(Topic src, TopicChanged tc) {
        DVar<bool> pin=src as DVar<bool>;
        int idx=-1;
        if(pin==null || tc.Initiator==_mnt) {
          return;
        }
        if(tc.Art==TopicChanged.ChangeArt.Remove) {
          for(idx=0; idx<_pins.Length; idx++) {
            if(_pins[idx]==pin) {
              _pins[idx]=null;
              ushort n_ipol=_ipol, n_iodir=_iodir;
              n_iodir&=(ushort)(~(1<<idx));
              _inps&=(ushort)(~(1<<idx));
              if(_iodir!=n_iodir) {
                _iodir=n_iodir;
                _flags|=4;
              }
              n_ipol&=(ushort)(~(1<<idx));
              if(_ipol!=n_ipol) {
                _ipol=n_ipol;
                _flags|=2;
              }
              break;
            }
          }
        } else {
          for(int i=0; i<_pins.Length; i++) {
            if(_pins[i]==pin) {
              idx=i;
              break;
            }
          }
          if(idx==-1) {
            ushort n_ipol=_ipol, n_iodir=_iodir;
            if(pin.name.Length==3 
              && (pin.name[0]=='I' || pin.name[0]=='O') 
              && (pin.name[1]=='p' || pin.name[1]=='n')
              && ((pin.name[2]>='0' && pin.name[2]<='9') || (pin.name[2]>='A' && pin.name[2]<='F'))) {
              idx=pin.name[2]-'0';
              if(idx>9) {
                idx-=7;
              }
              if(pin.name[0]=='I') {
                n_iodir|=(ushort)(1<<idx);
                _inps|=(ushort)(1<<idx);
              } else {
                n_iodir&=(ushort)(~(1<<idx));
              }
              if(_iodir!=n_iodir) {
                _iodir=n_iodir;
                _flags|=4;
              }
              if(pin.name[1]=='p') {
                n_ipol&=(ushort)(~(1<<idx));
              } else {
                n_ipol|=(ushort)(1<<idx);
              }
              if(_ipol!=n_ipol) {
                _ipol=n_ipol;
                _flags|=2;
              }
            } else if(pin.name=="IRQ") {
              if(pin.value && !_busy && _flags==0) {
                _pt=DateTime.Now.AddMilliseconds(1);
              }
              return;
            } else {
              return; // unknown variable
            }
            if(_pins[idx]!=pin) {
              if(_pins[idx]!=null) {
                _pins[idx].Remove(tc.Initiator);
              }
              _pins[idx]=pin;
            }
          }
        }
        if(pin.name[0]=='O') {
          ushort n_gpo=_gpo;
          bool val=((_ipol & (1<<idx))==0)?pin.value:!pin.value;
          if(val) {
            n_gpo|=(ushort)(1<<idx);
          } else {
            n_gpo&=(ushort)(~(1<<idx));
          }
          if(_gpo!=n_gpo) {
            _gpo=n_gpo;
            _flags|=1;
          }
        }
        if(!_busy && _flags!=0) {
          _pt=DateTime.Now.AddMilliseconds(1);
        }
      }
    }