bus control



	------------+---------------+---------------+------
		    |               |               |
		+---+---+	+---+---+	+---+---+
		|	|	|	|	|	|
		+---+---+	+---+---+	+---+---+
		    |               |               |
		    |               |               |
		+---+---+	+---+---+	+---+---+
		| 	|	|	|	|	|
		+-------+	+-------+	+-------+


with many devices on a bus, any device can pull a line low

leading to a possibly incorrect value and the inability

for other devices to communicate.


include buffer chips between the bus and each device, controlled

by the CPU or bus controller, to reduce/prevent this problem











