Values in new 24FC512
Just reporting some behaviour I cannot find in the datasheet - or anywhere! Had me scratching my head, and might save someone else doing the same?
Reading from a brand new (never written) Microchip 24FC512 gave the following results for a sequential read, anywhere in the array:
- first byte of any sequential read = 127 (7Fh)
- every subsequent byte = 255 (FFh)
So you can read either 7Fh or FFh from the same location, depending on whether it is the first byte in a sequential read or not.
Any written bytes behave exactly as expected - while any never-written bytes continue to show the above behaviour until written the first time (even when other parts of the array are written and behaving normally). So it seems the array has a special "factory" state that the chip can sense.
A full write to the entire array is needed to eliminate this state. Wish this detail was in the datasheet - it isn't in my version anyway.