Basic PIC 16C84 programmer for PC parallel port
          ===============================================
                 David Tait (david.tait@man.ac.uk)
                 =================================

          
          _____        _________
 13.8V   |     |  5V  |         |
  +--+---|78L05|--+---|1/4  4066|-----------------------------+
     |   |_____|  |   |_________|                             |
    _|_     |    _|_       |            ________________      |    100n
 10u___     |    ___100n   |          O| 1      U    18 |O    |    | |
     |      |     |        |          O|                |O    +----| |----+
    ///    ///   ///       |          O|                |O    |    | |    |
                           |    +-----O| MCLR/Vpp       |O    |   _____   |
           |\              |    |  +--O| Vss        Vdd |O----+--|_____|--+
  <D2>-----| >o--+---------+    |  |  O|            RB7 |O------+  10k    |
  (4)      |/    |  _____       | /// O|            RB6 |O----+ |        ///
                 +-|_____|--+   |     O|     16C84      |O    | |
 <GND>-------+       18k  13.8V |     O|________________|O    | |          
 (25)       ///   _________     |                             | |
                 |         |    |    _____                    | |
    13.8V +------|1/4  4066|----+---|_____|---+               | |
                 |_________|          10k     |               | |
           |\         |     _____            ///              | |
  <D3>-----| >o-------+----|_____|--+ 13.8V                   | |
  (5)      |/                18k                              | |
                       _____                                  | |
  LPT1             +--|_____|--+ 5V                           | |
           |\      |    10k                                   | |
  <D1>-----| >o----+------------------------------------------+ |
  (3)      |/          _____                                    |
                   +--|_____|--+ 5V                             |
           |\      |    10k                                     |
  <D0>-----| >o----+--------------------------------------------+
  (2)      |/                                                   |
                 All gates are inverting or non-inverting       |
            /|   TTL O/C buffers, 74xx06, or 74xx07             |
<-ACK>----o< |--------------------------------------------------+
 (10)       \|

  4066: pin-14, 13.8V; pin-7, GND.  buffer: pin-14, 5V; pin-7, GND.