Extra memory with a 24LC512?

Alex Mackinnon

I'm curious... is it possible to use a 24LC512 in place of the 24LC256 for the boot-time programme and an extra 32K of storage for programme use?

Does the Propeller check the chip version or is it happy with any serial EEPROM connected?

Has anyone tried it?

Peter Jakacki

The device address and access method are the same for the 256 and the 512, as it also is with many others. The Propeller tool will overwrite the first 32K when loading to eeprom but does not worry about anything after that. There is no "chip version" to check, it either has an eeprom at $A0 device address that has a valid boot image or it does not.

*Peter*

Alex Mackinnon

Cool. What I wanted and expected then [noparse]:)[/noparse] It should also work with a 24LC1025 if 32k extra storage is not enough [noparse]:)[/noparse])

BTW from you comment 'a valid boot image' can I assume that the image in EEPROM is checksummed/hashed/whatever to guard against executing a corrupted or invalid image? I don't see anything about that in the data I have downloaded.

Mike Green

There is a simple 8-bit checksum at location $05. Essentially, if you add up all the bytes in the initial RAM load from the Propeller Tool, the least significant byte should come out to zero. There's no checking when the EEPROM is loaded into RAM.

Newzed

Alex, I am using a 24LC512 in the Prop piggyback.· I start storing at 33000 - $80E8 - and it is working beautifully.· The Prop does not "see" anything above 32K so when I reload the program it has no effect on my storage area.· I'm storing the current address at 63000 - $F618 - which gives me 30,000 bytes of storage.· So far, that is more than enough.

Sid

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Alex Mackinnon

I can't wait for the chips to arrive so I can give it a go!