Yes, FM25V20 is obsolete. Yes, our newer Excelon family of F-RAM device CY15B104 or CY15V104 is superset of FM25V20. The code should work seamlessly. The following changes to be taken care in the software if used in current application.
1. Device ID should be updated for CY15B104 or CY15V104 based on the device used in the application
2. CY15B104QN, CY15V104QN, CY15B102QN, CY15V102QN doesn't support HOLD pin feature since this feature should be removed from the current software.
Also CY15FRAMKIT 002 SERIAL FRAM DEVELOPMENT KIT can be used to test the SPI functionality. QSPI device (CY15B104QSN-SXI) is mounted on the CY15FRAMKIT-002 Kit, which works in SPI, DPI, QPI mode. This device is superset of FM25V20A, CY15B104QN, CY15V104QN, CY15B102QN, CY15V102QN.