Toshiba TC9314F Manual

TC9314F2003-07-03583. CPU Stop Function, STOP Flip-Flop BitThe STOP flip-flop bit is set to “1” when the VDD voltage applied to the CPU falls below 1.5 V. Thisprevents CPU malfunction by shutting down the CPU. When a voltage of 1.5 V or less is applied to the V DDpin, the program counter stops and instruction execution ceases in the CPU.When a voltage higher than 1.5 V is again applied to the V DD pin, the CPU starts up again. As the CPUwas shut down, the clock and other timings are no longer valid. Use the STOP flip-flop to test whether theCPU stop function operated. Perform initialization or clock correction if required.The STOP flip-flop bit is reset to “0” whenever the RESET port 2 Hz flip-flop is set to “1”.Note 63: After a system reset or execution of the CKSTP instruction, the timer port and the STOP flip-flop arereset to “0”.Note 64: If the VDD voltage falls below 1.5 V when clock-stop mode is set, the CKSTP instruction cannot beexecuted. Be careful with the supply voltage timing, for example, when the radio is off.Note 65: The key scan data immediately after restarting the CPU are undefined.