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flash memory

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swathi

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hi,
i want to know the actual difference between flash memory , EEPROM and EPROM.
Also in the hardware part when do we say the pin is sinking or souring ??
For example in my recent project we have used a keyboard,LCD display.
In this case when i am sending a 0 to the port pin of the processor am i souring or sinking ??
Our ckt diagrams are present in the power point presentation attachment .
bye
 

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See basically Eprom stands for Erasable and Programmable ROM so you can erase and reprogram ROm using UV technique. The process of erasing and reprogrammin requires a seperate device so it's not used in applications where you need to do changes in memory frequently.

EEProm stands for electrically EProm so that u need not have any UV programmer for that. It can be erased using electrical signals but once again speed of the memory access is slow.

Flash overcomes disadvantages for low speed. It is semiconductor memory and a high speed one so suitable for programs using frequent read and write

89c51 has a built in Flash memory to store the program you write.
 
You should also be aware that many devices actually claiming to be 'FLASH', are in fact only 'EEPROM', FLASH is used more as a marketing name than anything else!.
 
swathi said:
hi,
i want to know the actual difference between flash memory , EEPROM and EPROM.
Visit www.atmel.com as they are the pioneers in flash technology. Briefing is already done by Piyush! And a punch by Nigel (I fully agree) as well :)
swathi said:
Also in the hardware part when do we say the pin is sinking or souring ??
Consider an NPN transistor connected to a supply by a pull up resistor and if you write one means 5 V to its base through base resistor, the voltage at its collector is 0V and if you give nothing (0V) at its base it becomes VCC. Simple Inverter ! In this case whatever be connected to the collector of that transistor will get either VCC or 0V. Now it always depends on the connections the way device is connected. It tells you the use of transistor either sinking or sourcing. If an LED is connected(One end to VCC through resistor and another to collector) to the transistor, it will be on only when base voltage is present, you call it logic 1. Thus transistor will complete the path for led and resistor circuit. And thus is sinking. Read 8051 literature carefully. It depends on how much your basics are cleared.
swathi said:
In this case when i am sending a 0 to the port pin of the processor am i souring or sinking ??
A zero on any port pin is always considered as ground. And thus sink path. For any uC and under any condition. :)

It seems you are a project partner of Prachi. :)
 
Nigel Goodwin said:
You should also be aware that many devices actually claiming to be 'FLASH', are in fact only 'EEPROM', FLASH is used more as a marketing name than anything else!.

how can we tell the difference between flash ande eprom if the market claims eeproms are flashes?
 
mstechca said:
Nigel Goodwin said:
You should also be aware that many devices actually claiming to be 'FLASH', are in fact only 'EEPROM', FLASH is used more as a marketing name than anything else!.

how can we tell the difference between flash ande eprom if the market claims eeproms are flashes?

For many purposes you don't need to!, but if you do then the programming of them is slightly different.
 
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