Check whether the module stop bit of the module stop control register (MSTPCRA, MSTPCRB, or MSTPCRC) is set to 0.
Setting the module stop bit to 0 enables access to the registers of the peripheral module.
After a reset is released, all modules other than the DMAC, DTC, and on-chip RAM are placed in the module stop state. No read/write access can be made to the registers of the module that are in the module stop state.
For more information, please refer to "Module Stop Function" and "Register Descriptions" sections in the "Power-Down Modes" chapter of the hardware manual."