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ST6215C Datasheet(PDF) 24 Page - STMicroelectronics |
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ST6215C Datasheet(HTML) 24 Page - STMicroelectronics |
24 / 105 page ![]() ST6215C/ST6225C 24/105 5.3 RESET 5.3.1 Introduction The MCU can be reset in three ways: s A low pulse input on the RESET pin s Internal Watchdog reset s Internal Low Voltage Detector (LVD) reset 5.3.2 RESET Sequence The basic RESET sequence consists of 3 main phases: s Internal (watchdog or LVD) or external Reset event s A delay of 2048 clock (fINT) cycles s RESET vector fetch The reset delay allows the oscillator to stabilise and ensures that recovery has taken place from the Reset state. The RESET vector fetch phase duration is 2 clock cycles. When a reset occurs: – The stack is cleared – The PC is loaded with the address of the Reset vector. It is located in program ROM starting at address 0FFEh. A jump to the beginning of the user program must be coded at this address. – The interrupt flag is automatically set, so that the CPU is in Non Maskable Interrupt mode. This prevents the initialization routine from being in- terrupted. The initialization routine should there- fore be terminated by a RETI instruction, in order to go back to normal mode. Figure 13. RESET Sequence VDD RESET PIN WATCHDOG VIT+ VIT- WATCHDOG UNDERFLOW RESET 2048 CLOCK CYCLE (fINT) DELAY LVD RESET INTERNAL RUN RESET RUN RUN RUN RESET RESET RESET 1 |