what is ROM? Rom(read only memory)

What is memory ?
types of memory?
what is ROM?
TYPES OF ROM

1. TOPIC ROM

2. Group Member ID Name 172-19-1998 Abdullahi Shire Ali 172-19-2000 173-19-2009 Mohamud abdi Osman Abdullahi Ismacil Presented Ms.Tasnuva Ali Assistant Professor  Dept. OF ETE Daffodil International University 153-19-1824 Tahmid Rahman Khan

3. Contents Introduction of memory History of Memory Types of memory and definition Types of Rom Faction of Rom Advantages and dis advantages of Rom Conculation

4. Introduction of memory A Memory is just like a human brain. It is used to store data and instructions.  Computer   memory  is any physical device capable of storing information temporarily like RAM (random access memory), or permanently, like ROM(read-only memory). Computer memory is the storage space in the computer, where data is to be processed and instructions required for processing are stored . The memory is divided into large number of small parts called cells. Each location or cell has a unique address, which varies from zero to memory size minus one.

5. History of Memory in the early 1940s, memory technology mostly permitted a capacity of a few bytes.  ENIAC(Electronic Numerical Integrator And Computer): Firs electronic general- purpose computer . That is capable of being reprogrammed to solve a large class of numerical problems The next significant advance in computer memory came with acoustic  delay line memory , developed by  J. Presper Eckert  in the early 1940s . Efforts began in the late 1940s to find  non-volatile memory .  Jay Forrester, Jan A. Rajchman  and  An Wang  developed  magnetic-core memory , which allowed for recall of memory after power loss.

6. Process of Memory Memory Input Output Processor Storage

7. Types of Memory E -ROM

8. What is Rom Memory Short for  read-only memory ,  ROM  is a  storage medium  that is used with computers and other electronic devices. As the name indicates, data stored in ROM may only be  read . Read-only memory  (ROM), also known as  firmware , is an integrated circuit programmed with specific data when it is manufactured . ROM chips are used not only in  computers , but in most other electronic items.

9. Cont.…………. Stores crucial information essential to operate the system, like the program essential to boot the computer. It is not volatile. Always retains its data. Used in embedded systems or where the programming needs no change. Used in calculators and peripheral devices. ROM is further classified into 4 types-  ROM ,  PROM ,  EPROM , and  EEPROM .

10. ROM at Work Similar to RAM and ROM chips is contain a grid of columns and rows. But where the columns and rows intersect, ROM chips are fundamentally different from RAM chips. RAM uses transistors to turn on or off access to a capacitor at each intersection, ROM uses a diode to connect the lines if the value is 1. If the value is 0, then the lines are not connected at all . If a diode is present at that cell, the charge will be conducted through to the ground, and, under the binary system, the cell will be read as being "on" (a value of 1).

11. Other Types of memory Faction PROM (Programmable read-only memory)  – It can be programmed by user. Once programmed, the data and instructions in it cannot be changed. EPROM (Erasable Programmable read only memory)  – It can be reprogrammed. To erase data from it, expose it to ultra violet light. To reprogram it, erase all the previous data. EEPROM (Electrically erasable programmable read only memory)  – The data can be erased by applying electric field, no need of ultra violet light. We can erase only portions of the chip.

12. PROM Work Creating ROM chips totally from scratch is time-consuming and very expensive in small quantities. For this reason, mainly, developers created a type of ROM known as programmable read-only memory (PROM ). PROM chips (Figure 2) have a grid of columns and rows just as ordinary ROMs do. The difference is that every intersection of a column and row in a PROM chip has a fuse connecting them . A charge sent through a column will pass through the fuse in a cell to a grounded row indicating a value of 1. Since all the cells have a fuse, the initial (blank) state of a PROM chip is all 1s. To change the value of a cell to 0, you use a programmer to send a specific amount of current to the cell. Figure About PROM

13. Applications of Programmable Read Only Memory (PROM) The Programmable ROM (PROM) are used in Mobile Phones for providing User Specific Selections. Video game consoles Implantable Medical devices. Radio-Frequency Identification (RFID)tags. High definition Multimedia Interfaces(HDMI)

14. Advantages and Disadvantage of Programmable Read Only Memory (PROM) The programming can be done using many types of software and does not rely on hard wiring of the program to the chip. Since it is not possible to un-blow the fuse, so the authenticity of the data remains intact and it is impossible to remove or alter the contents. The biggest disadvantage of PROM is that the data once burnt cannot be erased or changed when detected with errors.

15. EPROM Work Erasable programmable read-only memory (EPROM) addresses this issue . EPROM chips can be rewritten many times. . Erasing an EPROM requires a special tool that emits a certain frequency of ultraviolet (UV) light Once again we have a grid of columns and rows. In an EPROM, the cell at each intersection has two transistors. The two transistors are separated from each other by a thin oxide layer. One of the transistors is known as the floating gate and the other as the control gate

16. Cont.…………. Data can be extracted from the EPROM by decoding the address at the address pins and then connecting it to the output buffers.  The programming process in EPROM is not reversible electrically. Ultraviolet light is used to cause ionization within the oxide which allows the stored charge to dissipate and the memory is also deleted.

17. Applications of Erasable Programmable Read Only Memory (EPROM) As program storage chip in Micro controllers. For debugging. For program development. As BIOS chip in computers. As program storage chip in modem, video card and many electronic gadgets.

18. Advantages of EPROM EPROM is non-volatile so it retains its memory even without power. So no external memory is required. EPROM is quite effective. EPROM is reprogrammable i.e. the data in the EPROM can be erased and reprogrammed.

19. Disadvantages of EPROM Transistors used in EPROM have a higher resistance. The EPROM needs UV light to erase the data. This can’t be done using electrical signals. It is not possible to erase a particular byte of data in EPROM. The whole data is deleted. The static power consumption of EPROM is quite high. It takes some time to erase the data in EPROM. This is different than EEPROM where the data can be instantaneously erased.

20. EEPROMs Work EPROMs are a big step up from PROMs in terms of reusability, they still require dedicated equipment and a labor-intensive process to remove and reinstall them each time a change is necessary. Also changes cannot be made incrementally to an EPROM the whole chip must be erased. Electrically erasable programmable read-only memory (EEPROM) chips remove the biggest drawbacks of EPROMs

21. Cont.…………. The chip does not have to removed to be rewritten. The entire chip does not have to be completely erased to change a specific portion of it. Changing the contents does not require additional dedicated equipment.

22. Applications of Electrically Erasable Programmable Read Only Memory (EEPROM) As BIOS chip in computers As storage for re-programmable calibration information in test-equipment. As storage for in-built self learning functionality in remote operated transmitters.

23. Advantages of Electrically Erasable Programmable Read Only Memory (EEPROM) The method of erasing is electrical and instant. Chip can be reprogrammed infinite number of times. Byte wise data can be erased instead of entire content on the board. To change the data, additional devices are not required.

24. Disadvantages of Electrically Erasable Programmable Read Only Memory (EEPROM) Different voltages are required for erasing, reading and writing the data. The data retention period of EEPROM is limited i.e 10 years approx. EEPROM devices are expensive compared to others.