The FRAM operates at the bus speeds (I2C or SPI) and hence there is no timings defined. The max speed/frequency at which the I2C or SPI can be operated is mentioned in the datasheet. Say for example for SPI FRAM the max frequency for SPI protocol is mentioned as 40 MHz. Now the user can select any frequency upto 40 MHz. If some user user operates at 1 MHz he will observe faster read and write operations than a user who is operating at 500 KHz. So the timings are dependent on the speed grade you select for the protocol.