Hi all,
I'm seeing a strange bug with a flash chip. So far it's isolated but I was wondering if anyone has opinions about what might be happening here:
Chip: Spansion 32MBit
When I program certain sectors (3f8000,3fa000,3fc000,3fe000) they act like RAM. I can write data and read data back but when I power cycle the device the data is back to 0xFFFF...
I can think of a few explanations but I don't know enough about the inner workings of flash to know which ones to eliminate:
1) The chip is defective and acts like a RAM chip on those sectors 2) The sectors in question are write-protected and act therefore act like RAM 3) There's a defect on our PCB and I actually am writing to the SRAM chip sharing the address bus 4) There's a defect on the chip that causes the sectors to be erased each time the device powers upSome background:
- It's an FPGA based system with flash and SRAM sharing the bus.
- We don't have any high voltages hooked up to the flash chip so our only way of programming are the in-system CFI routines.
- The programming routines include a normal SRAM-like write cycle at the end so that would explain how it could look like SRAM
- So far only one of several devices exhibit the problem, all others work fine.
Thanks, Andrew