Monday, 15 January 2018

digital logic - How Does a Wired AND/OR Bus work


Studying for an exam Looking at Data buses using Wired AND and Wired OR configurations.



Using tristate logic, a device is able to gain control of the bus and transmit anything down it.


I don't understand Wired AND or Wired OR. The way I understand Wired AND at the moment - no device has control of the Bus and the output stays at a constant voltage (say 5V) if no devices are attempting to use the bus. However when a device attempts to use the bus the line will be pulled to 0V. Now if any device attempts to use the bus at the same time, it will never be clear which device is transmitting.


Also Wired AND is supposed to be active high however when a device uses the bus the line goes low. I would have thought this was active low.




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