We deal with erasing eproms with UV-C light in further detail below. With these chips, erasure is carried out by exposure to intensive ultraviolet light in the area of 254 nm wavelength. 'Erasable' means that the data on it can be removed. Each Byte has its own address, numbered from 00000h through FFFFFh (corresponding to the decimal 0 to 1048575).Īside from the 8 Bit memory chips, there are also 16 Bit memory chips, serial 1-Bit memory chips and (rarely/old) 4 Bit chips.ĮPROM stands for Erasable Programmable Read Only Memory. For example, in an 8-megabit chip like the 27c801, there are altogether 1048576 bytes (= 8388608 bits). The Bytes can be accessed at this address and then the eight bits of the accessed address are output on its eight data ports. Therefore a Kilobyte is 1024 Bytes and a Megabyte is 1048576 Bytes.įor the 8 Bit memory chips (the most common type) the Bits are put together in a Byte (= 8 bits) and stored under an 'address'. The terms Kilo and Mega with regard to Bytes were also adapted to the binary nature (zero or one) of the digital systems. We would like to direct those who need more precise information about the number systems to suitable other locations. Therefore, two digits can also accept 256 values (from 00h to FFh, wherein the small 'h' only identifies the hexadecimal number). This is based on a number of 16 and uses the digits 0 to 9 and additionally, A to F. In order to represent these, the hexadecimal number system is used. The most commonly used term is the Byte, which contains 8 bits and can accept 2 to the 8th power = 256 different values. Sixteen bits are a 'Word', eight bits are a 'Byte' and four bits are a 'Nibble'. It is difficult for a person to gain an overview over these Bits therefore, they are gathered into groups. A Bit can either be a zero (0) or a one (1). The program / data is stored in the memory chip by a series of numbers - zeros and ones (=bits). Data could consist, for instance, of temperature values taken by a temperature measurement system, or any other data. In this context, a program is a series of commands (command string) for a microprocessor (= computing unit).

Memory chip names and how to find replacement chipsĪ memory chip is an electronic component which can store a program, data or both.

Erasure of eproms with ultraviolet light.

In particular, we will discuss the various types of memory chips and compare what the 27C, 28C or 29F series, for instance, can and cannot do. For this reason, we are now making the basic information for programming memory chips, such as eproms/eeproms and Flash chips, public here.

We receive frequent inquiries on memory chips and are repeatedly forced to note that there is still a very high requirement for information in this area.

Basic information about memory chips and programming

27c256 eprom programmer