A ROM is a combinational component for storing data. The data might be a truth table or the data might be the control words for a microprogrammed CPU. A ROM that implements two functions does not require twice the number of gates as a ROM that implements one function. (The decoder is shared by every output function.)
we will design Read only memory using the circuits cloud simulator
if you does not used the circuits-cloud before, you can see this intractable:
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Step 1: The ROM Design
Because it is 16*8 ROM, it needs:
- 4 digital inputs
- 8 leds ( as output )
So, drag and drop the components from the digital components panel and connect them
Step 2: Store the Value in ROM Locations
1. Double click in ROM parameter.
2. write an 8-bit value in each location of ROM.
3. click on ( save parameter)
Step 3: Saving and Running the Circuit
save your circuit then running it.
check the output value in each address (location):
if input ( A0, A1, A2, A3 ) =
0000 , output = the value stored in location 0
1000 , output = the value stored in location 1
0100 , output = the value stored in location 2
1100 , output = the value stored in location 3
0010 , output = the value stored in location 4
and so on.
- you can check the circuit:
- also you can see how the circuit works.. in this video