參數(shù)資料
型號: S1C63408F0A0100
元件分類: 微控制器/微處理器
英文描述: MICROCONTROLLER, PQFP128
封裝: PLASTIC, QFP-128
文件頁數(shù): 77/151頁
文件大小: 1171K
代理商: S1C63408F0A0100
S1C63406/408 TECHNICAL MANUAL
EPSON
23
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Watchdog Timer)
4.2 Watchdog Timer
4.2.1 Configuration of watchdog timer
The S1C63406/408 has a built-in watchdog timer that operates with a 256 Hz divided clock from the
OSC1 as the source clock. The watchdog timer starts operating after initial reset, however, it can be
stopped by the software. The watchdog timer must be reset cyclically by the software while it operates. If
the watchdog timer is not reset in at least 3–4 seconds, it generates a non-maskable interrupt (NMI) to the
CPU.
Figure 4.2.1.1 is the block diagram of the watchdog timer.
Watchdog timer
Non-maskable
interrupt (NMI)
OSC1 dividing signal 256 Hz
Watchdog timer enable signal
Watchdog timer reset signal
Fig. 4.2.1.1 Watchdog timer block diagram
The watchdog timer contains a 10-bit binary counter, and generates the non-maskable interrupt when the
last stage of the counter (0.25 Hz) overflows.
Watchdog timer reset processing in the program's main routine enables detection of program overrun,
such as when the main routine's watchdog timer processing is bypassed. Ordinarily this routine is
incorporated where periodic processing takes place, just as for the timer interrupt routine.
The watchdog timer operates in the HALT mode. If a HALT status continues for 3–4 seconds, the non-
maskable interrupt releases the HALT status.
4.2.2 Interrupt function
If the watchdog timer is not reset periodically, the non-maskable interrupt (NMI) is generated to the core
CPU. Since this interrupt cannot be masked, it is accepted even in the interrupt disable status (I flag =
"0"). However, it is not accepted when the CPU is in the interrupt mask state until SP1 and SP2 are set as a
pair, such as after initial reset or during re-setting the stack pointer. The interrupt vector of NMI is
assigned to 0100H in the program memory.
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