Zone Sensor Controller

Eight of the PIC I/O lines are used as inputs. A pair of photo-transistors at a zone boundary are connected to two lines and make one zone sensor. This will give four zone sensors per card. The controller responds to the following commands. 
  Command    Function
  ---------  ---------------------------------
  0100 0000  Poll(respond with status byte)
On a poll command it returns one of the following two status bytes. 
  Response   Function
  ---------  ------------------------------------
  0010 0000  Entered zone to the left
  0010 0001  Entered zone to the right
  0010 0010  Left zone on left
  0010 0011  Left zone on right
  0010 0100  Presence on zone on left detected
  0010 0101  Presence on zone on right detected
  0010 0110  No status change since last poll
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Updated on 2 Nov 95. Feedback to