Decoder

Mano Section 4.9

Outline

• Decoder• Applications• Verilog

Example of a Decoder

Convert binary information from n input lines to 2n unique outputlines.

This particular circuit take a binary number and convert it to an octal number.

Hardware Implementation

AND and NOR Decoders

Take an n-bit address.Produce 2n outputs,One of which is activated.

(NOR Decoder)

Organization of Memory Systems

Basic SRAM and VTC

A wordline is used to select the cellBitlines are used to perform read and write operations on the cell

Cross Coupled Configuration

The cell can only flip its internal state when one of its internal cross VS.During a read op, we must not disturb its current state.During a write op, we must force the internal voltage to swing past VS to change a state.

A 2-to-4 decoder with Enable

(typo, should be a 0)

Demultiplexer

A Demux is a circuit that receives information from a singleline and directs it to one of 2n possible output lines.

Use a 2-to-4 decoder as a Demux

(typo, should be a 0)

Treat A and B as the selector bits. i.e. A and B select which bit should receive infomraiton.E is treated as the data line.

Implement a Full Adder with a Decoder

Build a Bigger Decoders

Use w to enable either top or bottom decoder.

3-to-8 decoder in verilog

3-to-8 decode

Input bits

Use a Test Bench to Generate output

Initial statements execute oncestarting from time 0.

$monitor: display variable whenever a value changes.$time display the simulation time

Run functional Simulation

Results