The rise in READ ONLY MEMORY applications has been exponential in nature.Presently there is hardly a new digital system that doesn't boast of a specification such as "microprogram controlled","new ROM or PLA has made this product reliable and economical," "microprocessor controlled",and so forth.The ROM,though simple in concept,had to wait until the semiconductor industry could produce these devices economically;since then they hence become one of the most widely used components ever produced.
A ROM is a "digital dictionary," a memory device whose output code is dependent on an input code.The ROM is sometimes referred to as READ ONLY - STORAGE,fixed memory,permanent storage,or dead memory,but basically it is an array-type multiple-output combinational circuit having basically the model shown in fig:
ROM's are characterized or specified by their "size" This size or bit number is determine by the following expression:
ROM size= 2^n X m
where n=number of inputs
m=number of outputs
For example, a ROM with ten inputs and eight outputs would be specified as an
8k ROM
1024 X 8 ROM
For example, a ROM with ten inputs and eight outputs would be specified as an
8k ROM
1024 X 8 ROM
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