Erasable PROM
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Introduction to EPROMs
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Good morning, class! Today, we’re diving into Erasable Programmable Read-Only Memory, or EPROM. Can anyone tell me what makes EPROM special?
Is it that we can erase and reprogram it?
Exactly! EPROM allows us to erase and reprogram data multiple times. It’s non-volatile which means it holds data without power. Student_2, can you explain how UV EPROMs work?
Sure! A UV EPROM uses ultraviolet light to erase the data stored on it.
Correct! It requires a special chip removal to expose it to UV light for erasure. This is an essential aspect of its design. What might be a limitation of this method?
It sounds inconvenient to have to remove the chip every time you need to erase it.
Great observation! That is indeed a significant drawback. Now let’s summarize: EPROMs store data indefinitely and can be erased and reprogrammed, but UV EPROMs need special handling for erasure.
EEProm Characteristics
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Now, let’s move on to electrically-erasable PROMs, or EEPROMs. Who can tell me how EEPROMs differ from UV EPROMs?
EEPROMs can be erased and reprogrammed while still in the circuit!
Exactly! This feature makes EEPROMs much more flexible to use. They have a different programming technique that allows individual byte erasure. Can anyone think of an application for EEPROM?
They might be used in computers to store firmware!
That’s right! Firmware often requires updates, and the ability to rewrite that memory without removing the chip is vital. Now let’s summarize today's session: EPROMs can be erased with ultraviolet light but need to be removed from the board, while EEPROMs allow functional in-circuit updates without removal.
Applications and Types
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Let’s explore where we commonly use EPROMs and EEPROMs. What are some areas?
They can be used in consumer electronics, like in appliances or cameras!
That’s spot on! Any specific examples, Student_3?
Maybe in a camera to store settings or preferences?
Correct! Their ability to retain data even without power makes them perfect for storing settings. Also, can anyone remember the difference in access speed between UV EPROMs and EEPROMs?
EEPROMs are generally slower, right?
Yes, EEPROMs typically have slower access times compared to UV EPROMs due to their unique programming and erasing methods. In summary, EPROMs find applications in a variety of devices for data retention due to their non-volatile nature.
Introduction & Overview
Read summaries of the section's main ideas at different levels of detail.
Quick Overview
Standard
Erasable PROMs, including UV EPROMs and EEPROMs, offer non-volatile storage with the ability to be erased and reprogrammed. UV EPROMs utilize ultraviolet light for erasure, while EEPROMs allow in-circuit electrical erasure and programming.
Detailed
Detailed Summary of Erasable PROM
Erasable Programmable Read-Only Memory (EPROM) is an essential type of non-volatile memory that allows users to erase and reprogram data on demand. Once programmed, EPROMs retain data indefinitely.
Types of EPROM
- Ultraviolet-Erasable PROM (UV EPROM): Uses a MOS transistor with a floating gate. A high-voltage programming pulse injects electrons into the floating gate, keeping the transistor in its 'on' state. Data can be erased by exposure to ultraviolet light, which removes the stored charge. This erasure process takes around 15-20 minutes and affects all memory cells simultaneously.
- Example chips: Intel's 2732, 2764, 27128.
- Disadvantages include the need to remove the chip for reprogramming and lack of selective erasure.
- Electrically-Erasable PROM (EEPROM): Similar in construction to UV EPROMs but allows for in-circuit erasure with a reversed voltage pulse on the chip. EEPROMs can erase and rewrite individual bytes without requiring removal from the circuit, making them more versatile than UV EPROMs. Despite their advantages, EEPROMs have higher costs and lower density than UV EPROMs.
Flash Memory
Flash memory can be considered a further development that combines features of both EPROMs and EEPROMs, providing high-density and high-speed storage with electrical erase options.
In summary, while EPROMs provide the flexibility of erasure and reprogramming not found in traditional PROMs, each type has its advantages and limitations, influencing their application in various computing scenarios.
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Overview of EPROM
Chapter 1 of 5
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Chapter Content
EPROM can be erased and reprogrammed as many times as desired. Once programmed, it is nonvolatile, i.e., it holds the stored data indefinitely. There are two types of EPROM, namely the ultraviolet-erasable PROM (UVEPROM) and electrically erasable PROM (EEPROM).
Detailed Explanation
An EPROM (Erasable Programmable Read-Only Memory) is a type of memory that can be erased and reprogrammed repeatedly. Nonvolatile means that the data is retained even when the power is turned off. There are two main types: UVEPROM and EEPROM, which differ in how they are erased and reprogrammed.
Examples & Analogies
Think of EPROM like a reusable whiteboard. You can write on it and then erase everything with a simple wipe. The UVEPROM is like using special lighting to erase the board while EEPROM allows you to erase specific parts without needing to wipe everything clean.
Ultraviolet-Erasable PROM (UVEPROM)
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The memory cell in a UVEPROM is a MOS transistor with a floating gate. In the normal condition, the MOS transistor is OFF. It can be turned ON by applying a programming pulse (in the range 10–25V) that injects electrons into the floating-gate region. These electrons remain trapped in the gate region even after removal of the programming pulse.
Detailed Explanation
In UVEPROM, the memory cell is designed with a special configuration using a MOS transistor which has a floating gate. When you apply a high voltage pulse, it allows electrons to get trapped in the floating gate, switching the MOS transistor ON. After the pulse is removed, the information remains stored because the trapped electrons keep the transistor in the ON state.
Examples & Analogies
This mechanism is like filling up a water balloon. When you apply pressure (the high voltage), the water (electrons) fills the balloon (floating gate). Even if you stop applying pressure, the water remains inside the balloon until you take the balloon outside in the sun (exposing to UV light), which causes the water to leak out and the balloon to shrink (erasure).
Erasing UVEPROM
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Chapter Content
The stored information can, however, be erased by exposing the chip to ultraviolet radiation through a transparent window on the top of the chip meant for the purpose. The photocurrent thus produced removes the stored charge in the floating-gate region and brings the transistor back to the OFF state.
Detailed Explanation
To erase the data stored in a UVEPROM, the chip must be exposed to UV light. This light causes a current that removes the electrons trapped in the floating gate, thus switching the MOS transistor back to its OFF state, effectively erasing the stored information.
Examples & Analogies
Imagine you have a chalkboard that writes with a special type of chalk which needs sunlight to be erased. The sunlight represents the UV light, and once it hits the chalkboard, all the writings disappear, just like the data in the UVEPROM when exposed to UV light.
Disadvantages of UVEPROM
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UVEPROMs suffer from disadvantages such as the need to remove the chip from the circuit if it is to be reprogrammed, the non-feasibility of carrying out selective erasure, and the reprogramming process taking several tens of minutes.
Detailed Explanation
UVEPROMs can be inconvenient because they must be physically removed from the circuit to be reprogrammed. Additionally, you can only erase all the data on the chip at once; you can't erase specific parts, which can be a limitation. The entire process can also be time-consuming.
Examples & Analogies
Consider a library where you can only return all the books at once and it takes a long time for the librarian to check in every book. You can't choose to return just one specific book quickly. This is how UVEPROMs operate—they can only erase all at once and take time to do so.
Electrically Erasable PROM (EEPROM)
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Chapter Content
The memory cell of an EEPROM is also a floating-gate MOS structure with the slight modification that there is a thin oxide layer above the drain of the MOS memory cell. Application of a high-voltage programming pulse between gate and drain induces charge in the floating-gate region which can be erased by reversing the polarity of the pulse.
Detailed Explanation
In contrast to UVEPROMs, EEPROMs use an electrically erasable method. Their memory cells can be reprogrammed in the circuit without needing to remove them. The floating gate still holds charge, but can now be manipulated electrically to change its state and erase information by applying a reversed voltage.
Examples & Analogies
Think of EEPROMs like a modern touchscreen tablet that allows you to update apps or files without taking it out of the case. You can easily select which app to update without resetting the entire tablet. This flexibility and speed set EEPROMs apart from UVEPROMs.
Key Concepts
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EPROM: A type of non-volatile memory allowing erasure and reprogramming.
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UV EPROM: Erasable with UV light, needs to be removed for erasure.
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EEPROM: Can be erased and reprogrammed in-circuit, storing data byte-by-byte.
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Flash Memory: A high-density form of non-volatile memory with fast erase options.
Examples & Applications
The Intel 2732 is a commonly used UV EPROM that stores up to 4K bits of data.
Smart cards use EEPROMs to store sensitive information securely with the ability for selective erasure.
Memory Aids
Interactive tools to help you remember key concepts
Rhymes
EPROMs hold your data tight, erase with UV, bring it back to light.
Stories
Imagine a library where every book can be erased and rewritten with new stories, like EPROMs doing their magic with data.
Memory Tools
Remember EEPROM: Easily Erased, Easy to Rewrite in the Outer Platform.
Acronyms
EEPROM
Electrically Erasable Programmable Read-Only Memory.
Flash Cards
Glossary
- EPROM
Erasable Programmable Read-Only Memory; a type of non-volatile memory that can be erased and reprogrammed.
- UV EPROM
Ultraviolet erasable programmable ROM; a type of EPROM that uses UV light for erasure.
- EEPROM
Electrically erasable programmable ROM; a type of memory that allows for in-circuit erasure and reprogramming.
- Flash Memory
A type of non-volatile memory that combines features of EPROMs and EEPROMs, allowing fast erase and write times.
Reference links
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