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SONIC the Hedgehog
02-23-2012, 12:50 AM
So I've been looking around for a 128k EEPROM, but I've found data sheets and one time write ROMs, but no DIP EEPROMs, so could anybody give a suggestion as a site I could find one, or a store I could find one at? Thanks a bunch!

Phil Pilgrim (PhiPi)
02-23-2012, 12:58 AM
128K bytes:


http://search.digikey.com/us/en/products/AT24C1024B-PU/AT24C1024B-PU-ND/1886125

Is this what you were looking for?

-Phil

SONIC the Hedgehog
02-23-2012, 01:02 AM
Yes actually thanks! I wonder how I didn't find that. Also, is there a spefic standard for the number of pins used in EEPROMs? I've seen some other ones with 40 pins, but would still be 128k and stuff like that.

Phil Pilgrim (PhiPi)
02-23-2012, 01:25 AM
The 40-pin devices are parallel versions, which have a separate pin for each address and data line. Parts that start with 24 are I2C serial and are always 8-pin devices; parts that start with 25 are SPI serial; parts that start with 93 are Microwire (or other 3-wire) serial.

-Phil

Bits
02-23-2012, 01:27 AM
The 40-pin devices are parallel versions, which have a separate pin for each address and data line. Parts that start with 24 are I2C serial and are always 8-pin devices; parts that start with 25 are SPI serial; parts that start with 93 are Microwire (or other 3-wire) serial.

-Phil

Wow this is good stuff. :smile:

SONIC the Hedgehog
02-23-2012, 01:44 AM
Originally Posted by Phil Pilgrim (PhiPi)
The 40-pin devices are parallel versions, which have a separate pin for each address and data line. Parts that start with 24 are I2C serial and are always 8-pin devices; parts that start with 25 are SPI serial; parts that start with 93 are Microwire (or other 3-wire) serial.

-Phil
Wow this is good stuff.

My thoughts exactly. Thanks for the help Phil, and I'm sure I will do something with a parallel device. Hurray for geniuses. :lol:

kwinn
02-24-2012, 01:10 AM
The more or less standard package for a 128K x 8 bit parallel memory is 32 pins. That would be 17 address, 8 data, 2 power, 1 chip select, 1 output enable, and 1 read/write. The remaining 2 pins are either unused or used as additional chip select/output enable pins. Typically smaller byte wide memories used a 28 pin package and word (16 bit data out) memories used a 40/44 pin package.

SONIC the Hedgehog
02-25-2012, 03:02 AM
The more or less standard package for a 128K x 8 bit parallel memory is 32 pins. That would be 17 address, 8 data, 2 power, 1 chip select, 1 output enable, and 1 read/write. The remaining 2 pins are either unused or used as additional chip select/output enable pins. Typically smaller byte wide memories used a 28 pin package and word (16 bit data out) memories used a 40/44 pin package.

Thanks that's helpful to know, but the one I looked at was an eight pin, and I plan on getting a data sheet too. Also, my friend has an old computer from the 90s that has removable DIP cache modules. Would it be possible to use it as workspace, or just impractical?

kwinn
02-25-2012, 06:00 AM
Thanks that's helpful to know, but the one I looked at was an eight pin, and I plan on getting a data sheet too. Also, my friend has an old computer from the 90s that has removable DIP cache modules. Would it be possible to use it as workspace, or just impractical?
The one you have is a serial memory where the data is read out 1 bit at a time. The ones in the old computers (8086/286/386/486 motherboards) were mostly 8 bit wide parallel chips and I did use them with Z80 and 6800 series micros so they should work. Of course you will need to use quite a few address and data pins to use them with a micro. A 32K x 8 bit chip needs 15 address, 8 data, and at least 3 control pins.

SONIC the Hedgehog
02-25-2012, 10:25 AM
Which pins on the prop would I need though? 30-31 doesn't seem to be enough, and 28-29'are for USB right?

Publison
02-25-2012, 04:11 PM
Which pins on the prop would I need though? 30-31 doesn't seem to be enough, and 28-29'are for USB right?

P30-31 are used for the USB interface. P28-29 are the I2C buss for the EEPROM.

If you take kwinn's example for a 32K x 8 bit parallel RAM chip, you would need 26 pins to communicate with the chip, (P0-P27).

I would look at the 24xxx series I2C as they only take two pins.

Jim

SONIC the Hedgehog
02-26-2012, 03:54 AM
P30-31 are used for the USB interface. P28-29 are the I2C buss for the EEPROM.

If you take kwinn's example for a 32K x 8 bit parallel RAM chip, you would need 26 pins to communicate with the chip, (P0-P27).

I would look at the 24xxx series I2C as they only take two pins.

Jim
I plan on sticking with that, but since the parallel RAM chip is RAM, could it be used as an address for hub ram?

Dr_Acula
02-27-2012, 03:05 AM
I plan on sticking with that, but since the parallel RAM chip is RAM, could it be used as an address for hub ram?

Yes. And you can expand hub memory that way. Cluso99 took this to extremes connecting a parallel ram chip to a propeller to run a Z80 emulation. Only trouble was there was only one pin left. But he then cleverly used to run a display on one pin.

There are lots of compromises - more prop pins = more speed. Latches to hold high addresses while you clock through 256 bytes etc.

The *clever* solution is to use slower serial ram and caching.

SONIC the Hedgehog
02-27-2012, 03:09 AM
Ah, thanks for explaining. Also I don't even know of the chip works! My friend took apart the computer and has the motherboard laying on the carpet.