Decoder
Mano Section 4.9
Outline
• Decoder
• Applications
• Verilog
Example of a Decoder
Convert binary information from n input lines to 2n unique output
lines.
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 cell
Bitlines 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 single
line and directs it to one of 2n possible output lines.
Use a 2-to-4 decoder as a
Demux
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.
(typo, should
be a 0)
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 once
starting from time 0.
$monitor: display variable whenever
a value changes.
$time display the simulation time
Run functional Simulation
Results