전자부품 데이터시트 검색엔진 |
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Q67127-C2060 데이터시트(PDF) 48 Page - Siemens Semiconductor Group |
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Q67127-C2060 데이터시트(HTML) 48 Page - Siemens Semiconductor Group |
48 / 85 page Semiconductor Group 48 1997-12-01 C505 / C505C C505A / C505CA Fail Save Mechanisms The C505 offers enhanced fail safe mechanisms, which allow an automatic recovery from software upset or hardware failure : – a programmable watchdog timer (WDT), with variable time-out period from 192 µs up to approx. 412.5 ms at 16 MHz. – an oscillator watchdog (OWD) which monitors the on-chip oscillator and forces the microcontroller into reset state in case the on-chip oscillator fails; it also provides the clock for a fast internal reset after power-on. The watchdog timer in the C505 is a 15-bit timer, which is incremented by a count rate of f OSC/12 upto f OSC/192. The system clock of the C505 is divided by two prescalers, a divide-by-two and a divide-by-16 prescaler. For programming of the watchdog timer overflow rate, the upper 7 bits of the watchdog timer can be written. Figure 24 shows the block diagram of the watchdog timer unit. Figure 24 Block Diagram of the Programmable Watchdog Timer The watchdog timer can be started by software (bit SWDT in SFR IEN1) but it cannot be stopped during active mode of the device. If the software fails to refresh the running watchdog timer an internal reset will be initiated on watchdog timer overflow. For refreshing of the watchdog timer the content of the SFR WDTREL is transfered to the upper 7-bit of the watchdog timer. The refresh sequence consists of two consequtive instructions which set the bits WDT and SWDT each. The reset cause (external reset or reset caused by the watchdog) can be examined by software (flag WDTS). It must be noted, however, that the watchdog timer is halted during the idle mode and power down mode of the processor. MCB03306 IP0 (A9 ) H OSC f WDTS 2 16 14 07 8 WDTL WDTH / 6 External HW Reset Control Logic IEN0 (A8 ) H IEN1 (B8 ) H 6 70 WDT Reset - Request WDTPSEL WDTREL (86 ) H WDT SWDT OWDS |
유사한 부품 번호 - Q67127-C2060 |
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유사한 설명 - Q67127-C2060 |
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