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C00002 00002				VENDING MACHINE INTERFACE
C00005 ENDMK
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			VENDING MACHINE INTERFACE
				By Ted Panofsky

	The Vending Machine Interface allows the PDP-10 to enable one
of  the  10  price  bars inside the vending machine.  Patch wires are
then installed on the price bars to enable the doors.  When a CONO to
the device is executed, the selected price bar is energized, enabling
all doors in that price range.  When a door is opened, the device  is
cleared,  disabling  all  doors  except the one opened.  That door is
then locked again when the column select button is pressed.

VMI IS DEVICE 364
CONO VMI,
or
CONI VMI,
	  ___ ___
	18   |
	19   |
	20___|
	21   |
	22   |	 UNUSED
	23___|
	24   |
	25   |
	26___|
	27   |___
	28   |
	29___|	 PRICE BAR NUMBER
	30   |	  [INVERTED BCD)
	31   |___
	32___|___VENDED/ENABLE
	33   |
	34   |	 PI CHANNEL
	35___|___

	The CONO should contain an interrupt channel, the  price  bar
number,  and the ENABLE bit.  When the customer has opened a selected
door and the machine has cleared itself, the VENDED bit will be  set,
and  the  device  will interrupt on the PI CHANNEL selected.  At some
future time, the high order 10 bits can be  used  for  some  sort  of
password arrangement.
	CAUTION:   If the computer is selecting a price bar and money
is  placed  in  the machine, two price bars will be enabled.   When a
door is opened that is selected by either bar, the vmi will  indicate
VENDED  and  the machine will also gobble the money, overcharging the
customer.