I have a FM25CL64B FRAM chip on my board - the FRAM chip does not respond to SPI at all. Vdd is at 3.305V and both WP and HOLD are tied to Vcc. We replaced a standard flash chip to try out this part - the controller to fram chip connections are good. Controller outputs to FRAM are all good - CS, SI and SCK all look good - except SO is held high. I have tried multiple SPI modes, inserted multiple ms delay before accessing the device, but nothing helped.
Would really appreciate any assistance in root causing this issue.
Sincere apologies for the delay.
Please clarify the below queries:
1.if your following tVR and tVF spec mentioned in the datasheet?
2.How many parts (FRAM devices)are failing ?
3. which flash device you are using ? what are the operations you are trying to perform?