Hi, Sivakrishna,
I have checked the pin assignment of MK66FN2M0VLQ18, the FB_CS1 is multiplexed with PTD0 pin, this is the process to configure the pin as FB_CS1.
1)enable PORTD clock by SIM_SCGC5|=0x01<<12;
2)configure MUX to configure the pin as FlexBUS
PORTD_PCR0&=~(0x07<<8);
PORTD_PCR0|=0x05<<8;
3)configure the FB_CS1 as FB_CS1 with the code
FB_CSPMCR|=0x01<<28; //set Group1 as 01;
4)set the FB_CSAR1 address as 0x6000 0000;
5)set the FB_CSMR1=0x01; //which is based on the size of external memory size for BAM bits, //set the bit0 as 1
6)set the other FB registers
Pls have a try.
Hope it can help you
BR
Xiangjun rong