Again about the Flash memory...
> Quoting directly from the Atmel data book, re their AT29C256...
> "PROGRAM: The device is reprogrammed on a page basis. If a byte
> of data within a page is to be changed, data for the entire page
> must be loaded into the device. Any byte that is not loaded
> during the programming of its page will be erased to FFh. Once
> the bytes of a page are loaded into the device, they are simul-
> taneously programmed during the internal programming period. After
> the first data byte has been loaded into the device, successive
> bytes are entered in the same way, Each new byte to be programmed
> must have its high-to-low transition on /WE (or /CE) within 150us
> of the low-to-high transition of /WE (or /CE) of the preceding byte.
> If a low-to-high transition is not detected within 150us of the last
> low-to-high transition, the load period will end and the internal
> programming period will start. A6 to A14 specify the page address.
> The page address must be valid during each high-to-low transition
> of /WE (or /CE). A0 to A5 specify the byte address within the page.
> The bytes may be loaded in any order, sequential loading is not
> required."
I have one question : After writing a byte into a specific location, is it
possible to erase this
single byte? This is because with the AMD flashes I use, you can use an
erase to set all
bits to '1' and you use the program to set certain bit's to '0'. As far as I
know a write action
does not set bit's from '0' to '1'.
If this is the way I think it is (just like above), it is not RAM.
I thought I have seen this 'problem' in the AMD devices (29F040, 512 kbyte,
8 bit).
It could be the software I wrote at that time was not correct. (Used it in a
Gameboy cartridge with
Flash memory. I programmed this cartridge with an adapter I made on my MSX)
Greetings from Erik Maas
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