This figure shows the block diagram of a typical WDT on an RX MCU. First notice that the WDT sits on the peripheral bus. At the bottom users will see the WINA and WINB registers that have arrows pointing to other watchdog timer registers. The reason for this will be discussed later. The other three watchdog timer registers are shown here. The TCNT is the watchdog timer counter register and RSTCSR and TCSR are registers for controlling the watchdog timer.