Issues with FRAM SPI communication

[Anonymous]

I'm trying to communicate with a CY15B104Q FRAM device over SPI and haven't been able to get it working. I've double and triple-checked all the pin mappings and verified the FRAM device is receiving power. I have the HOLD and WP pins tied to VDD. I've also tried 3 separate FRAM devices and had the same issue with each. I've checked the SPI signals I'm sending to the FRAM device on a scope and they all seem fine. I've tried performing a command to read the status register but can't even get that to work. The RDSR opcode shows correctly on the scope, and is timed correctly with the SI and CS lines, but no data comes back on the SO line from the FRAM device. Any ideas on what could be causing this issue?

[SudheeshK]

Hi,

Could you please attache the SPI waveform (all SPI signals) for RDSR command?

Thanks and Regards,

Sudheesh

[Anonymous]

Here are the images from the scope of the SPI waveforms. The second image is a zoomed-in view of the RDSR command.

[SudheeshK]

Hi,

The waveform looks fine. Are you following the "power cycle timing" specs mentioned in datasheet? Could you please check and confirm that the specs tPU, tPD, tVR and tVF are followed in your application? Power cycle timing specs are mentioned in page 16 of the datasheet (http://www.cypress.com/file/209146/download).

Thanks and Regards,

Sudheesh

[Anonymous]

Yes, the power specs conform to the datasheet. The power-up ramp rate is 55 us/V, the power-down rate is 3000 us/V, and tPU and tPD are well above the limits specified in the datasheet.

[GirijaC]

Hi,

I am the product application engineer for F-RAM and would like to assist you on this query.

I looked at the waveform and the signals looks fine. Please answer the following questions which will help to debug the issue in right direction,

1. Are you probing signals on the F-RAM device pin or on controller pins to capture the waveform?

If you are probing on controller pins, can you capture waveform on the F-RAM device pin.

2. From where did you source these ICs. Is it from our distributors?

3. Please share the marking information on the device. You can take  picture of the top marking on the device and share.

4. Is it possible to share the schematic? Is SPI signals are shared between any other IC's?

5. One way to test if part is good or bad is, you can lift the SO pin of the device on the board and probe that pin to see if you still see this issue. Lifting the pin will isolate if the issue with device or any other peripheral connected to it. Lifting pin is possible if you are using SOIC part.

Thanks,

Girija