   byte protocol; // Which protocol we're running, 255 = none
   byte runlevel; // Runlevel 0 = off, 1 = stim off, 2 = stim on pulse off, 3 = pulse on
   byte pin;      // The digital pin number for this output, or 255 = analog out
-  byte unused0;
+  byte disabled; // Channel may not be used unless it is 0
 };
 
 int proto_i = 0;

  if (running < 0) {
    msg[i++] = '!';
    for (int j = 0; j < errormsgN; j++, i++) msg[i] = errormsg[j];
  }
  else if (running == 0) {
    byte zero[] = "000000s000000u";
    for (int j = 0; j < (int)sizeof(zero); j++, i++) msg[i] = zero[j];
  }
  else {
    six_in(global_clock.s, msg + i);

  shiftbuf(2);
  halt_channels();
  running = -1;
  memcpy(errormsg, "unknown ", 8);
  memset(errormsg + 8, ' ', errormsgN - 8);
}

// Loop runs forever
