FRAM FM25CL64b non-responsive

[Anonymous]

Hello, 

   

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.

       

Thanks

[Anonymous]

Hi Santosh,

   

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?

   

Thanks,

   

Krishna.