Tricky FMC Question

[DOsbo]

When connecting a parallel FLASH device to the micro the address mappings are thus:

For a NOR FLASH device with an 8 bit data bus, the internal address (FMC_Ax) maps directly to the micro hardware pins (HW_Ax).

8-Bit Data Bus

FMC_A0 => HW_A0 ======> FL_A0

FMC_A1 => HW_A1 ======> FL_A1

.

FMC_A24 => HW_A24 ======> FL_A24

FMC_A25 => HW_A25 ======> FL_A25

For a NOR FLASH device with a 16 bit data bus, the micro shifts the internal address right 1 bit. Effectively, you get the mapping below:

16-Bit Data Bus

FMC_A1 => HW_A0 ======> FL_A0

FMC_A2 => HW_A1 ======> FL_A1

.

FMC_A25 => HW_A24 ======> FL_A24

???? =>HW_A25 ===?

My question is what signal is placed on HW_A25? If it's nothing, can that pin be re-assigned for a different function?

Cheers

David

[waclawek.jan · Accepted solution]

> My question is what signal is placed on HW_A25?

Probably a fixed level. Did not try.

> If it's nothing, can that pin be re-assigned for a different function?

 Yes; as any other pin you don't need (e.g. when using a smaller memory).

JW

[DOsbo]

Ok JW, thanks for your prompt reply.