M27C801-90F1

Memory: M27C801-90F1 Application Field and Working Principle

M27C801-90F1 is an 8 megabit (1 megabyte (Mbyte)) CMOS UV erasable programmable read only memory (EPROM). This type of a read only memory (ROM) uses an ultra-violet (UV) light to erase the programmed memory.

It is composed of a single 8 megabit memory device from STMicroelectronics, of which ninety-two thousand (92,000) bytes are available for the user, divided into eight separate segments. Central to the operation of this type of memory device is the use of non-volatile memory cells, which remain unchanged unless subjected to an electrical or UV source. The device comprises of a single 8-bit data output port and an active low write enable line, commonly referred to as WE. The power requirements of the device are 5V@110mA.

The applications of the M27C801-90F1 EPROM are many and varied, and often relate to software and embedded system requirements. This type of memory has the capability to store 64-bit instruction sets and is assigned to a programmable logic device such as a microcontroller (MCU) or microprocessor (MPU). Such methods of embedded system design, offer greater flexibility and increased resource utilization than standard microcontroller systems.

The working principle of the device is based upon a dynamic random access memory (DRAM) architecture and uses Fowler-Nordheim (FN) tunneling to store information. The device is programmed with a set of data, arranged in segments, which is then retained in non-volatile memory cells. When required, the data can be accessed by presenting an address (or addresses) with an associated data word, depending on the type of operation. The read operation requires only the address to be provided and the data word is returned to the calling program/process in response.

The write operation also presents an address and associated data, but also requires a write enable signal in order to safely update the memory array. The write cycle is initiated by providing the write enable signal (synchronized to the internal clock), followed by the address and associated data. The entire write cycle takes approximately 30 milliseconds and the device will not accept further write requests until the write cycle has been completed.

In applications where data retention is a primary requirement, it is important to note that the M27C801-90F1 EPROM retains stored data for an extended period of time when subject to normal operating conditions. The device guarantees a minimum data retention of 50 years and industry reports indicate that functional retention times greater than 10 years.

The efficiency of this device is further enhanced by the use of non-volatile memory cells that allow for repeatable data retention without the need for battery backup supplies. It is for this reason that the M27C801-90F1 is often regarded as a superior choice of memory device for mission critical applications.

Overall, the M27C801-90F1 from STMicroelectronics offers an excellent choice of non-volatile memory solution. The device provides a highly reliable ultra-violet erasable memory solution, capable of data retention times quoted at fifty (50) years. Used in an appropriate application, the device may therefore be considered as a long-term, reliable solution.