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发表于 2012-4-19 21:57:56
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今天我也遇到同样的问题,不过已解决。
Device Reset (in) and Watchdog Reset (out).
Device reset. XRS causes the device to terminate execution.The PC will point to the address contained at the location 0x3FFFC0. When XRS is brought to a high level, execution begins at the location pointed to by the PC. This pin is drive now by the DSP when a watchdog reset occurs. During watchdog reset, the XRS pin will be driven low for the watchdog reset duration of 512 XCLKIN cycles.
这是2812器件手册里对复位管脚的表述。意思是这个管脚作输入时是复位引脚,作输出时是看门狗复位输出。
在看门狗复位期间,XRS将被拉低,并持续512个XCLKIN时钟。(应该是512个OSCCLK,即512个晶振时钟)
至于周期4.4ms,应该是系统上电(无程序时)后,看门狗启动,8位计数器计数满后产生一个复位信号。
例如用27MHz的晶振,就将检测出一个18.9us的低电平信号,周期大概是(参看器件手册看门狗一节)
27MHz/512=52734.375Hz,
(1/52734.375)*256 = 4.8ms。
所以,要是不能进入仿真环境的话,还是要注意电源纹波。 |
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