{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

lecture23

# lecture23 - Recall Tri-State Gates b A tri-state gate has...

This preview shows pages 1–2. Sign up to view the full content.

CMPT 150 Registers Page 1 Connecting registers to each other box5 Remember that RTL micro-operations involve moving data between registers and/or memory box5 Implementing micro-operations requires connections among the referenced registers and memory locations box5 One option is to make each connection in an ad-hoc manner: box5 CMPT 150 Registers Page 2 The Bus box5 A bus is an n-bit data highway box5 With on and off ramps for every register box5 Registers share same wires for all connections R0 box5 We want the bus to behave as follows: box5 Only one register can output at a time box5 Zero or more inputs can be active at once R1 R2 R3 CMPT 150 Registers Page 3 Implementing a Bus box5 We can implement an 8-bit bus using a mux: R0 R1 Eightuple 4x1 S 0 S 1 box5 Notice: box5 Only one registers data appears on the bus at one time box5 Zero or more registers can read the data on the bus R2 R3 Mux CMPT 150 Registers Page 4 Recall: Tri-State Gates box5 A tri-state gate has three “values”

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

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...
View Full Document

{[ snackBarMessage ]}

### Page1 / 2

lecture23 - Recall Tri-State Gates b A tri-state gate has...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online