EPROM
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An EPROM, or erasable programmable read-only memory, is a type of programmable read-only memory (PROM) chip that retains its data when its power supply is switched off. Computer memory that can retrieve stored data after a power supply has been turned off and back on is called non-volatile. It is an array of floating-gate transistors individually programmed by an electronic device that supplies higher voltages than those normally used in digital circuits. Once programmed, an EPROM can be erased by exposing it to strong ultraviolet (UV) light source. EPROMs are easily recognizable by the transparent fused quartz window on the top of the package, through which the silicon chip is visible, and which permits exposure to ultraviolet light during erasing.
An EPROM: the Texas Instruments TMS27C040, a CMOS chip with 4 megabits of storage and 8-bit output (shown here in a 600-mil ceramic dual-in-line package). The TMS27C040 operates at 5 volts, but must be programmed at 13 volts.
An Intel 1702A EPROM, one of the earliest EPROM types (1971), 256 by 8 bit. The small quartz window admits UV light for erasure.
Atmel AT27C010 - an OTP EPROM
K573RF1
Memory cell (computing)
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The memory cell is the fundamental building block of computer memory. The memory cell is an electronic circuit that stores one bit of binary information and it must be set to store a logic 1 and reset to store a logic 0. Its value is maintained/stored until it is changed by the set/reset process. The value in the memory cell can be accessed by reading it.
Layout for the silicon implementation of a six transistor SRAM memory cell.
32x32 core memory plane storing 1024 bits of data.
Intel 1103, a 1970 metal-oxide-semiconductor (MOS) dynamic random-access memory (DRAM) chip.
Die of the MT4C1024 (1994) integrating one-mebibit of DRAM memory cells.