parallel eeproms and 8051

Hi..

Im new to embedded systems, iv started with the 89c51 uC. Ive never used a parallel eeprom with the 89c51, thought iv used a serial one with the i2c protocol (and had a tough time in getting the thing to work, using sdcc :-( ).

My question is..can only a parallel eeprom be used to extend the RAM?? seems logical, or else how would the uC generate the address on its own??

Also, can some part of the code be in the on-chip flash and the remaining in an external serial eeprom?? again, how then would the uC know the address to find the remaining lines of code?

Finally, could u point me to some good places where i can find info on interfacing the 8051 types to a serial eeprom. How about bus arch too..

Im googling for this info too, in case u plan to flame me for not doing that :-)

Thanx in anticipation

Mayank

Reply to
funkymunky
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Only parallel EEPROMs can be used to extend the "native" RAM. Serial EEPROMs are pretty much just nonvolatile storage devices.

Not in a serial EEPROM, unless you load the code out of the EEPROM and into RAM for execution.

Your brain. Just study the serial EEPROM data sheet and think about how to bit-bang it (or get an 8051 with an SPI port and use a compatible EEPROM).

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Tim Wescott
Wescott Design Services
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Reply to
Tim Wescott

okay okay...i got that..another question:

out of i2c and spi, which standard is more popular? any specific reasons for it?

Reply to
funkymunky

Okay, got that..one more thing: out of spi and i2c, is any one of them more popular...if yes, why?

Reply to
funkymunky

No, because they address different concerns. Depending on the project one may have occasion to use SPI, I2C or both.

If you want to hook up a small, fixed number of peripherals to a microprocessor then SPI is much simpler to use. If you want to hook up a large number, or an unknown number, of peripherals to a microprocessor then I2C can't be beat.

Of course sometimes you have a peripheral that you must use that only comes with one interface, and then you're stuck.

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Tim Wescott
Wescott Design Services
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Reply to
Tim Wescott

Look at the vendors web sites [Atmel, Ramtron etc ] and you get an idea of what is available( and thus consumed ). i2c uses fewer pins, so you can get SOT23 i2c memories, but i2c tops out at 400KHz/1MHz/3.4MHz, with very few devices around that work to the latest 3.4MHz ( I have not seen a uC yet that specs to 3.4Mhz i2c)

SPI is much faster, so can go to 50MHz on newest devices. So, for the largest memories, that need wider pipes, SPI is more common than i2c.

Sometimes, you can find both: the AT17F FPGA loader devices from Atmel, pgm like i2c, but read like SPI...

-jg

Reply to
Jim Granville

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