Hello Pramod,,
If you have enabled the peripheral in Sleep Mode and device has gone into sleep mode then the peripheral will remain active for any data transaction in sleep mode.
To make sure that the device is in Sleep Mode you can use the register SYSCTL.LDOSPCTL by writing the value 0x80000012 to it. Do make sure that you run the System Clock at 20MHz. When the device does go into Sleep Mode the VDDC pin will drop to 0.9V and will come back to 1.2V on an Interrupt/Reset.
It is also important to note that the CCS Debugger needs to be disconnected so that the register takes effect.
Regards
Amit
