EEPROM Memory

[GatorGuy]

I am looking into EEPROM memory from Microchip and would like to get some input on how they work. Does anyone have any schematics on how to connect them to a PIC? Also do they hold there memory when their power is cut or do they empty it?

 

[Jay.slovak]

I am looking into EEPROM memory from Microchip and would like to get some input on how they work. Does anyone have any schematics on how to connect them to a PIC? Also do they hold there memory when their power is cut or do they empty it?

Why would you like to do that? If your answer is you need more space than Internal EEPROM, that's ok. If not, Internal PIC EEPROMs have a capacity of 256-512 Bytes, that's pretty much. What do you want to store there?
Also, try tu use Internal Program memory to do the job, it's ususally pretty empty and is very fast.
If you still want to use external EEPROM, use one with SPI(25xxx) or I2C(24xxx) serial bus connection.

Ofcourse they Don't "forget" when power is removed.

 

[GatorGuy]

Pretty much to just add more memory. At this point it is only research. I am learning what I can now for future projects. For now internal memory is enough for what I need to do. But I might see a need for it later.

 

[Jay.slovak]

Pretty much to just add more memory. At this point it is only research. I am learning what I can now for future projects. For now internal memory is enough for what I need to do. But I might see a need for it later.

Oh I see, that's alright.

 

[Agent 009]

I encountered this problem with my recent project, if u remember Jay... I needed much more memory, so I had either to get EEPROM or shorten the program... I chose the latter one, though my teacher stated that it isn't hard to work with EEPROMs: connect'em from PIC ports to pins, looking at teh datasheet (obviously) of the EEPROM...

 

[Jay.slovak]

I encountered this problem with my recent project, if u remember Jay... I needed much more memory, so I had either to get EEPROM or shorten the program... I chose the latter one, though my teacher stated that it isn't hard to work with EEPROMs: connect'em from PIC ports to pins, looking at teh datasheet (obviously) of the EEPROM...

Yep I do...

Using external serial memory is not hard, but You should have some experiences before you do so.

 

[Agent 009]

Trial and error is the key :wink: ...
No really, I think the datasheet and knowing assembly would just do

 

[upand_at_them]

The serial EEPROMs have an I2C interface, which is really easy...just two pins and resistor pullups. I have some JAL code if you want to look at it.

Mike

 

[Agent 009]

I2C... Is that serial communication?

 

[Jay.slovak]

I2C... Is that serial communication?

Yes, it is 2wire, Half-Duplex synchronus serial communication in speeds from 100Khz thru 400Khz to 1Mhz max.

 

[Agent 009]

But my PIC is driven by a 4MHz oscillator... What 2 do???

 

[williB]

agent009 he said Kilo HZ not MHZ
a 4 mhz PIC should be able to handle 100 KHZ easily..

 

[Jay.slovak]

agent009 he said Kilo HZ not MHZ
a 4 mhz PIC should be able to handle 100 KHZ easily..

Or you can use PIC with I2C peripheral, and that very easy and fast.

 

[Agent 009]

agent009 he said Kilo HZ not MHZ
a 4 mhz PIC should be able to handle 100 KHZ easily..

Yeah, but if he said from 100Khz thru 400Khz to 1Mhz max... 4 MHz in not included???

 

[Jay.slovak]

agent009 he said Kilo HZ not MHZ
a 4 mhz PIC should be able to handle 100 KHZ easily..

Yeah, but if he said from 100Khz thru 400Khz to 1Mhz max... 4 MHz in not included???

That's not PIC frequency, it's the BUS speed.

 

[Agent 009]

So what's the difference :? :!: :!:

 

[Jay.slovak]

So what's the difference :? :!: :!:

That's VERY different! PICs frequency is simple how fast PIC works, you know that. But I2C clock is different, It is synchronising every bit on the I2C bus, and therefore it defines the transfer speed...

 

[Someone Electro]

Can it then transfer 1Mbit/s if its run at 1Mhz?
:shock:

thats about 100 KB/s and thats fast enugh for digital audio transfer.

Is it realy that fast?

 

[Jay.slovak]

Can it then transfer 1Mbit/s if its run at 1Mhz?
:shock:

thats about 100 KB/s and thats fast enugh for digital audio transfer.

Is it realy that fast?

Yes, if you run I2C at its max (1Mhz), it will transfer aprox. 128KB/s...

BTW: If speed is desired, you can use SPI @ 10Mhz, now that's fast!.

 

[Nigel Goodwin]

Can it then transfer 1Mbit/s if its run at 1Mhz?
:shock:

thats about 100 KB/s and thats fast enugh for digital audio transfer.

Is it realy that fast?

I suspect there are a number of conflicting and confusing thoughts in this thread!.

Firstly, I get the impression that the original question was asking about adding PROGRAM MEMORY to a PIC? - you can't do this for almost all PIC's, and I2C EEPROM wouldn't be suitable anyway. I2C EEPROM would only add another form of slow EEPROM data memory.

Secondly, I2C is a relatively slow system, designed for a very specific purpose (connecting IC's together on large PCB's, using just two wires on a common bus). As such, it's fairly slow and complicated (it was never designed to be fast!) - but as it's a syncronous system the speed of it is totally dependent on the speed of the master clock thats feeding the slaves - AS LONG AS THE SLAVE CAN KEEP UP!.

I2C EEPROM's are slow devices, you can read them a LOT faster than you can write them - and there are various projects available that can playback audio from an EEPROM using a PIC - but they use various clever methods to overcome the limitations. But you can't record the audio data in real time, the EEPROM is far too slow.