深入理解ARM体系架构（S3C6410）---S3C6410复位

S3C6410X has three types ofreset signals and SYSCON can place the system into one of three resets.

• Hardware reset: It isgenerated by asserting XnRESET. It is an uncompromised, ungated, total andcomplete reset that is used when you do not require information in system anymore. It fully initializes all system.

• Watchdog reset: It isgenerated by a special hardware block, i.e., watchdog timer. When the system ishanged due to an unpredictable software error, the hardware block monitorsinternal hardware status and generates reset signal to escape from this status.

• Wakeup reset: It is generatedwhen S3C6410X wake up from SLEEP mode. Since internal hardware states are notavailable any more after SLEEP mode, they must be initialized.

Hardwarereset

当XnRESET 引脚被声明后，系统内的所有单元（除了RTC 之外）复位到预先定义好的状态时，硬件复位被调用。在这段期间，将发生下面的动作：所有内部寄存器和ARM1176 内核都到预先定义好的复位状态。所有引脚都得到它们的复位状态。当XnRESET 被声明的同时，XnRSTOUT 引脚就被声明了。

XnRESET是不被屏蔽的，始终保持使能状态。XnRESET 的声明，无论先前为何模式，S3C6410 都进入复

位状态。XnRSET 必须持有足够长的时间允许内部稳定和传播。

The hardwarereset is invoked when XnRESET pin is asserted and all units in the system(except RTC) are reset to pre-defined states. During this period, the followingactions occur.

• All internalregisters and ARM1176 core go to the pre-defined reset states.

• All pins gettheir reset state.

• XnRSTOUT pinis asserted when XnRESET is asserted.

XnRESET isun-maskable and is always enabled. Upon assertion of XnRESET, S3C6410X entersinto reset state regardless of the previous mode. XnRSET must be held longenough to allow internal stabilization and propagation of the reset state toenter proper reset state.

Powerregulator for S3C6410X must be stable prior to the deassertion of XnRESET.Otherwise, it may damage S3C6410X and the operation is unpredictable. Figure3-17 is the timing diagram of power-on reset and pll turn-on sequence.

Watchdogreset

当软件挂起时，看门狗复位被调用。因此，在看门狗不能及时喂到时，就会发出超时命令。在看门狗复位期间，有以下动作发生：

除了ALIVE 和RTC 模块，所有模块进入预先定义好的复位状态。所有引脚都进入复位状态。在看门狗复位期间，nRSTOUT 引脚被声明。

在正常模式和闲置模式下，看门狗可被激活，并可产生超时信号。当看门狗定时器超时并复位使能时，其

可被调用。因此，下列依次发生：

1） WDT 产生超时信号。

2） SYSCON 调用复位信号，初始化内部IP。

3）包括nRSTOUT 复位被声明，直到复位计数器RST_STABLE 被终止。

Watchdog resetis invoked when a software hang-up. Then, the software cannot initialize aregister within WDT and WDT makes time-out signals for watchdog reset. As theoccurrence of watchdog reset means that system has fatal problem, it behaveslike external reset except reset status register. During the watchdog reset,the

followingactions occur:

• All blocksexcept reset status register in ALIVE block go to their pre-defined resetstate.

• All pins gettheir reset state.

• The nRSTOUTpin is asserted during watchdog reset.

Watchdog resetcan be activated in NORMAL and IDLE mode, since WDT can generate time-outsignal. It is invoked when watchdog timer and reset are enabled. Then, thefollowing sequence occurs:

1. WDTgenerate time-out signal.

2. SYSCONinvokes reset signals and initialize internal IPs.

3. The resetincluding nRSTOUT will be asserted until the reset counter, RST_STABLE, isexpired.

Wakeupreset

Wakeup reset is invoked whenS3C6410 is woken-up from SLEEP by a wakeup event. The details are described inSLEEP mode section.