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Unformatted text preview: Recall: Tri-State Gates b A tri-state gate has three “values” b Output is zero, one, or nothing b Nothing means open circuit (i.e. high impedance) b Tri-state buffer b One data input and one control input b If C=1 then output = input b If C=0 then output = disconnected CMPT 150 Registers Page 5 Tri-state Bus b We can implement a bus using tri-state buffers as follows: 2x4 Dec S S 1 CMPT 150 Registers Page 6 RTL and the Bus b Transferring to and from the bus can be done explicitly b We can treat the bus as a globally-connected register called “BUS” b E.g. write A b B as: b If the bus is known to exist, we can use it implicitly b I.e. we can just write A b B b Are the following expressions legal with a single shared bus?: A b B, C b B A b B, B b C A b B, B b A...
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- Spring '08
- SEPTA Regional Rail, Input/output, Jaguar Racing