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SM89516 Datenblatt(PDF) 9 Page - SyncMOS Technologies,Inc |
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SM89516 Datenblatt(HTML) 9 Page - SyncMOS Technologies,Inc |
9 / 19 page SyncMOS Technologies International, Inc. SM89516 8-Bits Micro-controller With 64KB flash & 1KB RAM embedded Specifications subject to change without notice contact your sales representatives for the most recent information. Ver 2.1 SM89516 08/2006 9 Extension Function Description 3.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 form 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. The SM89516 WDT has selectable divider input for the time base source clock. To select the divider input, the setting of bit2~bit0 (PS2~PS0) OF Watch Dog Timer Control Register (WDTC) should be set accordingly. The WDT is enable by setting 1 to the bit 7 (WDTE) of WDTC. After WDTE set to 1, the 16-bit counter starts to count with the selected time base source clock which set by PS2~PS0. It will generate a reset signal when overflows. The WDTE bit will be cleared to 0 automatically when SM89516 been reset, either hardware reset or WDT reset. To reset the WDT is done by setting 1 to the bit 5 (CLEAR) of WDTC. This will clear the content of the 16-bit counter and let the counter re-start to count from the beginning. 3.1 Watch Dog Timer Registers: WDT Control Register (WDTC, $9F) bit-7 bit-0 WDTE R Clear Unused Unused PS2 PS1 PS0 Read / Write: R/W - R/W - - R/W R/W R/W Reset value: 0 * 0 * * 0 0 0 WDTE : Watch Dog Timer enable bit CLEAR : Watch Dog Timer reset bit PS2~PS0 : clock source divider selection bit PS [2:0] Divider (OSC in) Time Period (ms) @40MHz 000 8 13.1 001 16 26.21 010 32 52.42 011 64 104.8 100 128 209.71 101 256 419.43 110 512 838.86 111 1024 1677.72 4. Reduce EMI Function The SM89516 allows user to reduce the EMI emission by setting 1 to the bit 0 (ALEI) of SCONF register. This function will inhibit the clock signal in Fosc/6Hz output to the ALE pin. This function is available when there is no external program memory or no external data RAM in the system. |
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