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A programmable read-only memory (PROM) is non-volatile semiconductor memory that is programmed after the chip is manufactured. A conventional PROM is supplied blank, programmed once, and then keeps its data without power. “Read-only” describes its normal use after programming—not the fact that it cannot be written at all.
How a PROM stores data
A conventional PROM stores its bit pattern using programmable elements such as fuse links. A PROM programmer applies controlled electrical pulses to selected cells, changing their link pattern to encode data. On a fuse PROM, that change is irreversible: the programmed contents cannot be erased to make the chip blank again.
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Exactly how a physical link maps to a binary zero or one depends on the device. Some designs represent a blown-open link as zero and an intact link as one, but that polarity is not universal.
Programming is separate from reading. Once programmed, the PROM can be read during normal use, and its contents persist when power is removed. That persistence is what makes it non-volatile, unlike ordinary volatile RAM.
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- Organization: 64Kx8
- Memory Density: 512Kbit
- Maximum Random Access Time: 70ns
- Output Enable Access Time: 40ns
- Package: DIP-28
How PROM differs from other ROM types
The key distinction is when the data is set and whether the memory can be erased and reused.
| Memory type | When and how it is programmed | Can it be erased and reused? |
|---|---|---|
| Mask ROM | Data is set during chip manufacture. | Not through ordinary user programming. |
| One-time PROM | Supplied blank and programmed after manufacture, commonly by changing fuse links with a programmer. | No. Fuse changes are irreversible. |
| EPROM | Programmed electrically; the erasable design is cleared with ultraviolet light. | Yes, after erasure. |
| EEPROM | Programmed and erased electrically. | Yes. |
PROM is sometimes used broadly when discussing programmable ROM families, including erasable types. In the narrower, conventional sense, however, PROM means a one-time-programmable device; EPROM and EEPROM are distinct erasable families, not synonyms for one-time PROM.
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- Product Type :Electronic Component
- Package Dimensions :1.193 Cm L X2.311 Cm W X9.398 Cm H
- Country Of Origin :Taiwan
- Package Quantity :1
What a PROM programmer does
A PROM programmer is the equipment used to write data to a compatible chip. The term describes a category of tool, not a universal device: programming requirements vary with the exact memory part. Before using or buying a programmer, confirm that it supports the chip’s part number, package, and programming requirements. The definition of PROM alone does not identify a compatible model.
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The Computer History Museum records that Radiation Inc. introduced a 512-bit bipolar TTL user-programmable ROM in 1970. Designers entered code by burning metal fuse links with an external programming unit, and the device could be used once only (Computer History Museum).
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- EEPROM Memory Chip Assortment
- 60 pcs, 6 types, 10 pcs each
- 24C02, 24C04, 24C08, 24C16, 24C32, 24C64
- 256B, 512B, 1MB, 2MB, 4MB, 8MB
- SOP-8 Package
The museum also documents Intel’s 2048-bit 1702 EPROM from 1971. Unlike a one-time fuse PROM, it could be reused after ultraviolet erasure (Computer History Museum).
Quick Recap
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- 1.The SOP8 clip enables in-circuit programming of for EEPROM without disassembling the chip, making flashing the BIOS simpler and more efficient.
- 2.The main purpose of the CH341A Programmer is to back up, erase, program, calibrate and other actions on various software.
- 3.SOIC8 SOP8 Test Clip For EEPROM 24CXX / 25CXX / 93CXX in-circuit programming
- 4.The CH341A Programmer support most 24 / 25 Series for EEPROM BIOS SOP8 SOP16 chip on the market. Note: Due to the characteristics of the CH341A chip, the ESMT SST class 25 chip can only be read and cannot be written.
- 5.5.Tips: Some chips are affected by peripheral circuits and cannot be clipped directly. Please check the chip location on the motherboard before purchasing!
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