Odd EPCS Silicon ID Reading

[Altera_Forum]

Hi folks, 

 When attempting to read the Silicon ID of an EPCS64 flash, I start by sending these four bytes (MSbit first): 0xAB, 0x00, 0x00, 0x00.   I can see that the EPCS64 drives data on the 32nd clock, but what I read is not the expected 0x16, but 0x08. If I read again, I get 0x20, and once more yields 0x82. It turns out that if I keep reading, this pattern repeats itself forever (i.e. 0x08 0x20 0x82 0x08 0x20 0x82...)   Analyzing this a bit further reveals that it's a bitstream with one bit high, five bits low, one bit high, five bits low, etc.   I have absolutely no clue why this happens.   Hope you can help me out here.    Thanks in advance. René Schipp von Branitz Nielsen

[Altera_Forum]

Something seems to be wrong with your method to interface the chip, either hard- or software. Without knowing the details, the reason can hardly be guessed. Seeing a signature length of 6 instead of 8 (it is repeated by design) suggests some kind of double clocking, e.g. due to signal integrity issues. 

 Frank