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SM79108L25 датащи(PDF) 6 Page - SyncMOS Technologies,Inc |
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SM79108L25 датащи(HTML) 6 Page - SyncMOS Technologies,Inc |
6 / 25 page Specifications subject to change without notice,contact your sales representatives for the most recent information. 6/26 Ver 2.1 SM79108 08/2006 SyncMOS Technologies International. Inc. SM79108 1. Watch Dog Timer The Watch Dog Timer (WDT) is a 16-bit free-running counter that generate reset signal if the counter overflows. The WDT is useful for systems which are susceptible to noise, power glitches, or electronics discharge which causing software dead loop or runaway. The WDT function can help user software recover from abnormal software condition. The WDT is different from Timer0, Timer1 and Timer2 of general 8052. To prevent a WDT reset can be done by software periodically clearing the WDT counter. User should check WDR bit of SCONF register whenever unpracticed reset happened The purpose of the secure procedure is to prevent the WDTC value from being changed when system runaway. There is a 250KHz RC oscillator embedded in chip. Set WDTE = “1” will enable the RC oscillator and the frequency is inde- pendent to the system frequency. To enable the WDT is done by setting 1 to the bit 7 (WDTE) of WDTC. After WDTE set to 1, the 16-bit counter starts to count with the RC oscillator. It will generate a reset signal when overflows. The WDTE bit will be cleared to 0 automatically when SM79108 been reset, either hardware reset or WDT reset. To reset the WDT is done by setting 1 to the CLEAR bit of WDTC before the counter overflow. This will clear the content of the 16-bit counter and let the counter re-start to count from the beginning. 1.1 Watch Dog Timer Registers: Watch Dog Key Register - (WDTKEY, 97H) By default, the WDTC is read only. User need to write values 1EH, 0E1H sequentially to the WDTKEY(97H) register to enable the WDTC write attribute, That is MOV WDTKEY, # 1EH MOV WDTKEY, # E1H When WDTC is set, user need to write another values E1H, 1EH sequentially to the WDTKEY(97H) register to disable the WDTC write attribute, That is MOV WDTKEY, # E1H MOV WDTKEY, # 1EH Addr SFR Reset 7 6 5 4 3 2 1 0 0E2H LCDB1 00H SEG2 SEG2 SEG2 SEG2 SEG3 SEG3 SEG3 SEG3 0E3H LCDB2 00H SEG4 SEG4 SEG4 SEG4 SEG5 SEG5 SEG5 SEG5 0E4H LCDB3 00H SEG6 SEG6 SEG6 SEG6 SEG7 SEG7 SEG7 SEG7 0E5H LCDB4 00H SEG8 SEG8 SEG8 SEG8 SEG9 SEG9 SEG9 SEG9 0E6H LCDB5 00H SEG10 SEG10 SEG10 SEG10 SEG11 SEG11 SEG11 SEG11 0E7H LCDB6 00H SEG12 SEG12 SEG12 SEG12 SEG13 SEG13 SEG13 SEG13 bit-7 bit-0 WDT KEY7 WDT KEY6 WDT KEY5 WDT KEY4 WDT KEY3 WDT KEY2 WDT KEY1 WDT KEY0 Read / Write: W W W W W W W W Reset value: 0 0 0 0 0 0 0 0 |
Аналогичный номер детали - SM79108L25 |
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Аналогичное описание - SM79108L25 |
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