IDXCHAN.2 State Machine Tables

  This is the truth table associated with the state machine
  implemented in the drawing IDXCHAN.2. The inputs are:
      I:  Interrupt Acknowledge (INTA)
      R:  Running
  The state variables are:
      n:  Not Requested (nrqd)
      s:  Serviced

   R I n s     n s      n    n 0 0 1 1
   ---------+-----           s 0 1 1 0
   0 0 0 0  |  0 0      R I  +--------
   0 0 0 1  |  1 1      0 0  | 0 1 1 0         _        _
   0 0 1 0  |  0 0      0 1  | 0 0 1 1   n+ = RI + In + Is
   0 0 1 1  |  1 1      1 1  | 0 0 1 1
   0 1 0 0  |  0 1      1 0  | 1 1 1 1
   0 1 0 1  |  0 1      
   0 1 1 0  |  1 0      
   0 1 1 1  |  1 1      s    n 0 0 1 1
   1 0 0 0  |  1 0           s 0 1 1 0
   1 0 0 1  |  1 0      R I  +--------
   1 0 1 0  |  1 0      0 0  | 0 1 1 0         _   _
   1 0 1 1  |  1 0      0 1  | 1 1 1 0   s+ = In + Rs
   1 1 0 0  |  0 1      1 1  | 1 1 0 0
   1 1 0 1  |  0 1      1 0  | 0 0 0 0
   1 1 1 0  |  1 0
   1 1 1 1  |  1 0