Lpc2000

> BTW is it possible to use internal ram of LPC2138 in Non volatile mode with
> RTC battery?

AFAIK it is not.
As for the cost and availability of FRAM, here in Russia I have found Ramtron's FM25L04 (512 bytes) for as low as $0.85 by the piece and in-stock, it may be different for your place though.

Regards,
  Max