Hi Rakesh,
Please ensure that all the AC timing and DC voltage requirements are met. Note that the SC18IC600 is compatible with SPI Mode 3 which means that the SCLK signal should be idle high and data is clocked in and out on the rising clock edge.

Please also ensure that the tSPILEAD and tSPILAG timing requirements are met.
Best regards,
Tomas