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Interactive Audio Lesson
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Introduction to PROM
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Today, we'll be talking about Programmable ROM, or PROM. Can anyone tell me how PROM differs from standard ROM?
Is it because PROM can be programmed by users?
Exactly! PROM allows users to set the data according to their needs using a PROM programmer. Now, why do you think this is beneficial?
Maybe because it saves money for custom applications?
Right! It's more cost-effective for single-run custom solutions! Just remember, once programmed, PROM cannot be changed.
Construction of PROM
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Next, let's talk about the construction of PROMs. Who can describe what a basic PROM memory cell looks like?
Doesnβt it use fusible links in its memory structure?
Yes! Each memory cell has fusible links that can be burned to create the necessary data representation. Anyone know how this process works?
You send a current through the link to store a '0' by blowing the fuse!
Perfect! This 'blowing' creates a permanent state in the device, either as a '1' or a '0'.
Applications of PROM
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Can anyone think of applications where PROM may be useful?
Firmware storage in devices?
Yes! It's commonly used to store firmware in embedded systems. So, summarizing, why would we choose PROM over other types?
It's cheaper for one-time programming, and itβs customizable!
Exactly! Great job! Just remember, the one downside is that we can't change it once set!
Introduction & Overview
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Quick Overview
Standard
Programmable ROM (PROM) is a type of ROM that allows users to program its contents using a PROM programmer. Unlike mask-programmed ROMs, which are permanently programmed during manufacturing, PROMs enable the customer to set the data at their convenience, albeit without the ability to erase and reprogram it. This section highlights the construction, working mechanism, and basic components involved in PROM technology.
Detailed
Programmable ROM (PROM)
Programmable ROM, or PROM, represents a significant advancement in the flexibility of Read-Only Memory. Unlike traditional ROM that is fixed at the manufacturing stage (mask-programmed ROM), PROM can be programmed by the user. This capability opens avenues for developers to tailor the ROM contents to their specific needs.
The programming is executed using a specialized device called a PROM programmer, allowing users to configure the memory by blowing fuses in the ROM to represent '1's and '0's. Each fuse link represents a specific storage capability, and once the programming is completed, the stored data is permanent, as they cannot be erased or modified after this point. PROMs have similar memory cell architectures to their mask-programmed counterparts and share common advantages, such as cost-effectiveness for custom ROM solutions. However, they also come with limitations, including their irreversibility and lack of rewritability. Overall, PROMs suit applications where a one-time programmable solution is ideal, such as firmware storage in devices.
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Introduction to Programmable ROM
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In the case of PROMs, instead of being done at the manufacturerβs premises during the manufacturing process, the programming is done by the customer with the help of a special gadget called a PROM programmer.
Detailed Explanation
Programmable ROM (PROM) allows users to program the memory contents themselves using a tool known as a PROM programmer. Unlike mask-programmed ROM, where the content is set during manufacturing, PROM gives flexibility to customers to define what goes into the memory at a later stage. This is especially useful for applications where the exact data requirements may change or where customization is necessary.
Examples & Analogies
Imagine a bakery that usually makes cookies using a standardized recipe. However, sometimes, customers want to add their own flavors or ingredients. The bakery can prepare a 'cookie-making machine' that allows customers to select their flavors using a programming device, just like a PROM programmer, making it possible to customize each batch of cookies on-demand.
Characteristics of PROM
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Since the data, once programmed, cannot be erased and reprogrammed, these devices are also referred to as one-time programmable ROMs.
Detailed Explanation
Once you program a PROM, the information is set permanently; this means that it cannot be changed or modified later. This quality is useful for certain applications where the data will not need to be altered, ensuring that the intended information remains intact throughout the device's lifecycle. This makes PROMs reliable for fixed-function applications where data stability is essential.
Examples & Analogies
Think of a photo printed on paper. Once it's printed, the information captured in the photo is fixed and cannot be changed unless you print a new one. Similarly, once data is programmed into a PROM, it remains unchanged, just like that permanent photograph.
Memory Cell Structure of PROM
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The basic memory cell of a PROM is similar to that of a mask-programmed ROM. Figures show a MOSFET-based memory cell and bipolar memory cell respectively. In the case of a PROM, each of the connections that were left intact or open in the case of a mask-programmed ROM are made with a thin fusible link.
Detailed Explanation
A PROM's memory cell can be built using various technologies such as MOSFETs or bipolar transistors. The programming process involves breaking a fusible link to register a '0' instead of a '1', allowing the device to store the intended data. The fusible link acts as a switch that can be turned off permanently once programmed.
Examples & Analogies
Consider a light switch that can either be in the 'on' position or 'off' position. When you flip the switch to 'off', it stays that way until physically changed again. In this analogy, programming a PROM is like flipping this switch to 'off', permanently setting that position and making it impossible to turn it back without replacing the switch.
Programming a PROM
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The programming operation is done with a PROM programmer. The PROM chip is plugged into the socket meant for the purpose. The programmer circuitry selects each address of the PROM one by one, burns in the required data and then verifies the correctness of the data before proceeding to the next address.
Detailed Explanation
Using a PROM programmer, individual addresses in the memory chip are accessed sequentially, and data is written to them. This process involves sending enough current through the fusible link to open it at specific locations on the chip, effectively programming the data in. After programming, the system performs checks to ensure that the correct data was stored, confirming the operation's success before moving onto the next piece of data.
Examples & Analogies
Think of a series of envelopes containing personalized letters for different individuals. Each envelope represents an address in the PROM. Just as you would individually write a letter and place it in the corresponding envelope, the PROM programmer meticulously writes data to each address in the memory, ensuring that every 'letter' is placed correctly before sealing it up.
Types and Applications of PROM
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PROM chips are available in various word sizes and capacities. 27LS19, 27S21, 28L22, 27S15, 24S41, 27S35, 24S81, 27S45, 27S43 and 27S49 are respectively 32Γ8, 256Γ4, 256Γ8, 512Γ8, 1KΓ4, 1KΓ8, 2KΓ4, 2KΓ8, 4KΓ8 and 8KΓ8 PROMs.
Detailed Explanation
PROMs come in different configurations, allowing for different amounts of data storage. The numerals represent the number of bits in each word and the total number of words available. For instance, a 32Γ8 PROM means there are 32 words, each 8 bits long, allowing the storage of 256 bits of data in total.
Examples & Analogies
Consider a library where each book represents a word in the PROM. Each book can have a specific number of pages (bits). A library arrangement with many small books will yield a large collection (more total data storage), while one large book would limit the diversity of information stored, just like varying sizes and configurations of PROM chips determine how much data they can hold.
Access Time for PROM
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The typical access time in the case of these devices is in the range 50β70 ns. MOS PROMs are available with much greater capacities than bipolar PROMs.
Detailed Explanation
Access time is an essential factor in memory devices as it represents how quickly data can be retrieved once requested. The specified range of 50β70 nanoseconds indicates that PROMs can access and deliver stored information relatively fast, making PRAM suitable for various applications where speed is necessary.
Examples & Analogies
Think of a vending machine. When you press a button, you anticipate receiving your snack quickly. If the machine takes too long, it's frustrating. PROMs with quicker access times function similarly, providing a response almost instantaneously within the set range of nanoseconds, allowing systems to operate efficiently.
Definitions & Key Concepts
Learn essential terms and foundational ideas that form the basis of the topic.
Key Concepts
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PROM: A type of ROM that can be programmed by users once.
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Fusible Link: A feature that enables the programming of PROM by burning connections.
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Differences from Mask ROM: PROM cannot be erased while mask ROM is permanently programmed.
Examples & Real-Life Applications
See how the concepts apply in real-world scenarios to understand their practical implications.
Examples
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An example of a PROM is used in microcontroller firmware where the code must remain unchanged after initial programming.
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In production lines, PROMs can quickly read data encoded for each specific run or batch.
Memory Aids
Use mnemonics, acronyms, or visual cues to help remember key information more easily.
π΅ Rhymes Time
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In PROM you'll see, data is stuck, burning links keeps it up, no programmability luck!
π Fascinating Stories
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A programmer setting up a smart device uses PROM to ensure the device always remembers its code, just like a student can't change their exam score after it's written.
π§ Other Memory Gems
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P-R-O-M: Programmable, Read-only, One-time, Memory.
π― Super Acronyms
F-L-I-P
- Fusible Links Indicate Programming in PROM.
Flash Cards
Review key concepts with flashcards.
Glossary of Terms
Review the Definitions for terms.
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Term: PROM
Definition:
Programmable Read-Only Memory, a type of ROM that can be programmed by the user but cannot be erased or reprogrammed.
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Term: PROM Programmer
Definition:
A device that allows users to program a PROM by setting the data stored in the ROM.
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Term: Fusible Link
Definition:
A thin connection in a PROM that can be blown to store a logical '0' by burning the link.
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Term: Maskprogrammed ROM
Definition:
A type of ROM that is programmed during manufacturing and cannot be modified afterward.