Page 117 - Digital Electronics by harish

Figure : Organization of four byte PROM

This process is also known as burning of PROM. The PROMs are one-time
programmable. Once programmed, the information stored is permanent. The blown fuse
stores a „1‟. The fuse uses materials like nichrome and polycrystalline.

Comparison between ROM and PROM

S. No. ROM PROM
1. Non-programmable. Programmable.
Flexible (Field-Programmable i.e.
Not flexible (because data
2. can be programmed in any place
can't be changed.
of work).
3. It is comparatively slower. It is comparatively faster.
Economical only when Economical even when produced
4.
produced in large volumes. in small volume.
Mainly used for research and
5. Used in PC's.
development purpose.
Writing of cells done by
6. Mainly done electrically.
'masking‟ mechanisms.

Table : ROM vs PROM

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