Connecting Flash to Coldfire FlexBus

[stephen_kainec]

We been using a Numonyx PC28F128J3F75A flash part with the flash part in x16 mode with the Cold chip select configured as a 16bit port. The address lines go from A0 to A0, A1 to A1, etc.  But on the Numonyx flash part, when in x16 mode, A0 is not used, so A1 is the lowest address line it uses.   Since this part is going end of life, we need to switch to another flash part and are looking at Micron MT28EW128ABA.   This flash part use A0.  The question is, if we just shift the address lines, have the Coldfire A1 go to the flash part A0, Coldfire A2 go to the flash part A1, etc.  Is this all we need to do to get the new flash part working like the old flash part or is there more to it, like perhaps the Numonyx interface is doing something we don’t realize and this is why it works?

[TomE]

They have horribly different pinouts, don't they? I thought all these chips had the same JEDEC-specified pinouts, but these two sure are different. Isn't there a pin-compatible one you can get?

The PC28F128J3F75A documents "A0" as only used in 8-bit mode. So the address lines in 16 bit mode go from A1 to A21 (32M), A22 (64M) or A23 (128M).

The MT28EW128ABA has address pins "A-1", A0, A1 ... A23 for 256M. Yes, Address Pin "minus one". They're not expecting it to be used in 8-bit mode, are they?

You don't need to "shift" connections as such. The pins with the same functions on the two chips just have different names. You'll just have to make sure things line up properly on the schematic.

Tom

[stephen_kainec]

We could not a pin compatible flash that worked like Numonyx flash, the couple of we found seemed all to work llike the Micron.   The Micron can be used in x8 mode or x16 mode.  The Numonyx flash we are using now is in x16 mode.  The issue we have is it seems the Coldfire treats each address as a byte where as the Micron treats each address as a word.  So were are thinking by not using the Coldfire A0 line, and having the Coldfire A1 to the flash A0, Coldfire A2 going to the flash A1, etc.  This should work, it is kind of how the Numonyx flash works now, since it does not use A0 but we still have the Coldfire A0 going to it.