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Z8F082ASH020SC 参数 Datasheet PDF下载

Z8F082ASH020SC图片预览
型号: Z8F082ASH020SC
PDF下载: 下载PDF文件 查看货源
内容描述: Z8喝采XP -R F08xA系列与扩展外设 [Z8 Encore XP-R F08xA Series with eXtended Peripherals]
分类和应用: 微控制器和处理器外围集成电路光电二极管时钟
文件页数/大小: 244 页 / 2750 K
品牌: ZILOG [ ZILOG, INC. ]
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Z8 Encore! XP® F08xA Series  
Product Specification  
79  
Watch-Dog Timer  
Overview  
The Watch-Dog Timer (WDT) protects against corrupt or unreliable software, power  
faults, and other system-level problems which may place the Z8 Encore! XP® F08xA  
Series devices into unsuitable operating states. The Watch-Dog Timer includes the follow-  
ing features:  
On-chip RC oscillator  
A selectable time-out response: reset or interrupt  
24-bit programmable time-out value  
Operation  
The Watch-Dog Timer (WDT) is a retriggerable one-shot timer that resets or interrupts the  
Z8 Encore! XP® F08xA Series devices when the WDT reaches its terminal count. The  
Watch-Dog Timer uses a dedicated on-chip RC oscillator as its clock source. The Watch-  
Dog Timer operates in only two modes: ON and OFF. Once enabled, it always counts and  
must be refreshed to prevent a time-out. Perform an enable by executing the WDT instruc-  
tion or by setting the WDT_AO Flash Option Bit. The WDT_AO bit forces the Watch-  
Dog Timer to operate immediately upon reset, even if a WDT instruction has not been  
executed.  
The Watch-Dog Timer is a 24-bit reloadable downcounter that uses three 8-bit registers in  
the eZ8 CPU register space to set the reload value. The nominal WDT time-out period is  
described by the following equation:  
WDT Reload Value  
-------------------------------------------------  
WDT Time-out Period (ms) =  
10  
where the WDT reload value is the decimal value of the 24-bit value given by  
{WDTU[7:0], WDTH[7:0], WDTL[7:0]} and the typical Watch-Dog Timer RC oscillator  
frequency is 10KHz. The Watch-Dog Timer cannot be refreshed after it reaches 000002H.  
The WDT Reload Value must not be set to values below 000004H. Table 55 provides  
information about approximate time-out delays for the minimum and maximum WDT  
reload values.  
PS024705-0405  
P R E L I M I N A R Y  
Watch-Dog Timer