Name– study of diode matrix ROM.
Aim – to study the process of memory storage and memory address locations.
Apparatus – rectifier diodes, circuit board, DC power supply, resistors, connecting wires, soldering iron, cutter etc.
Circuit diagram –
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Brief theory – a read only memory (ROM) can store thousands of binary numbers representing computer instructions and data. Some of the smaller ROMs are also used to implement truth tables. Therefore, a ROM can be used to generate any Boolean function. Suppose we want to build a circuit that stores the binary numbers as per given values. To keep tract of where the numbers are stored, we assign locations called addresses.
For example, we want to store 1101 at address–0, 1010 at address–1 and so on. Then the above circuit shows this combination. It shows a method to store the nibbles (group of 4–bits) as per given values. When the switch is in position–0, the first row of diodes is turned on so that the output of the ROM is Y3Y2Y1Y0 = 1101 and so on.
Conclusion –
1) The data can be stored into the memory locations of the ROM as required.
2) By selecting the proper address the stored data can be read from the memory of the ROM.
3) By changing the positions of diodes in the circuit, the data can be altered in particular memory location.