Microprocessor Memory: Read Only Memory

MICROPROCESSOR MEMORY:- Read Only Memory Home

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Parameters
Default Values 0011 1100 1001 0110
User Inputs

Programming a ROM (Read Only memory) permanently writes a data state (logic 1 or logic 0) to each memory location or cell.

Here we are using random binary 0 and 1 for each cell, generated by a Re-Program operation. In practice each cell is manufactured as logic 1 (diode present). A cell is then programmed to logic 0 as required by fusing the diode connection, shown here as a greyed-out device.

Reading is a measurement of the voltage developed across the Data resistor due to the current flowing through a good-diode. An open circuit diode will produce logic 0 as no current flows to generate a voltage or logic level across the resistor for that particular data line.

Note that a HIGH data output can only be derived from the logic 1 output of the 2 - 4-line decoder when that line is selected, this is because the decoder provides the 5V to bias on the good-diode.

TEST YOUR UNDERSTANDING: Probably the most important developments that have been in computer technology in recent years has been in computer memory devices.

Describe one single overriding thing that has changed in your view over the past decade. There will be several depending upon what application you are interested in.