How many times can a PROM be programmed?

Never, it is set at manufacture

What is the structure of a PROM?

Fixed AND array and programmable OR array with fusible links

Programmable AND array and fixed OR array

Floating-gate MOSFETs erased by UV

How is a 0 stored in a PROM bit?

A high current pulse blows the fuse

Electrons are injected into a floating gate

A mask leaves out the connection at manufacture

2081 Baisakh · 2 marks

Short note: PROM

Short answer

PROM is a one-time programmable ROM with a fixed AND array (decoder) and a programmable OR array of fusible links. All cells initially store 1; blowing selected fuses creates 0s. It stores fixed programs and implements combinational logic.

Write a short note on PROM.

PROM (Programmable Read-Only Memory) is a ROM that is manufactured blank and can be programmed once by the user with a PROM programmer. After programming its contents cannot be changed (one-time programmable, OTP).

Structure: a fixed AND array (decoder producing all minterms of the address lines) and a programmable OR array. Each cross-point has a fusible link (nichrome or polysilicon fuse, or a diode).
Programming: all fuses are intact at first (all bits 1). A high current pulse blows selected fuses, making those bits 0. This is permanent.
Uses: storing fixed programs, look-up tables and code converters; it can implement any combinational function in sum-of-minterms form.

Unlike EPROM or EEPROM, a PROM cannot be erased; a mistake means a new chip.

✓ Answer checked by Claude Opus 5.5 (high effort)

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