参数资料
型号: AT85C51SND3B1-7FTUL
厂商: Atmel
文件页数: 93/119页
文件大小: 0K
描述: IC DECODER/ENCODER DGTL 100CBGA
标准包装: 90
类型: 音频编码器/解码器
应用: 移动电话,手机,视频显示器
电压 - 电源,数字: 1.65 V ~ 3.6 V
安装类型: 表面贴装
封装/外壳: 100-TFBGA
供应商设备封装: 100-CTBGA(9x9)
包装: 托盘
75
AT85C51SND3B
7632D–MP3–01/07
Watchdog Timer
The AT85C51SND3B derivatives implement a hardware Watchdog Timer (WDT) that
automatically resets the chip if it is allowed to time out. The WDT provides a means of
recovering from routines that do not complete successfully due to software or hardware
malfunctions.
Description
The WDT consists of a 14-bit prescaler followed by a 7-bit programmable counter. As
shown in Figure 42, the 14-bit prescaler is fed by the WDT clock detailed in
The Watchdog Timer Reset register (WDTRST, see Table 89) provides control access
to the WDT, while the Watchdog Timer Program register (WDTPRG, see Figure 90) pro-
vides time-out period programming.
Three operations control the WDT:
Chip reset clears and disables the WDT.
Programming the time-out value to the WDTPRG register.
Writing a specific 2-Byte 1Eh-E1h sequence to the WDTRST register clears and
enables the WDT.
Figure 42. WDT Block Diagram
Clock Controller
As shown in Figure 43 the WDT clock (FWDT) is derived from either the peripheral clock
(FPER) or the oscillator clock (FOSC) depending on the WTX2 bit in CKCON register.
T h e s e c l o c k s a r e i s s u e d f r o m t h e C l o c k C o n t r o l l e r b l o c k a s d e t a i l e d i n
Section “Oscillator”, page 28. When WTX2 bit is set, the WDT clock frequency is fixed
and equal to the oscillator clock frequency divided by 2. When cleared, the WDT clock
frequency is equal to the oscillator clock frequency divided by 2 in standard mode or to
the oscillator clock frequency in X2 mode.
Figure 43. WDT Clock Controller and Symbol
WTO2:0
WDTPRG.2:0
WDT
CLOCK
÷
6
System
1Eh-E1h Decoder
WDTRST
14-bit Prescaler
RST
7-bit Counter
RST
To internal
EN
RST
MATCH
SET
OV
OSC
CLOCK
RST
Pulse Generator
reset
Reset
PER
CLOCK
WDT
CLOCK
OSC
CLOCK
0
1
WTX2
CKCON.6
÷
2
WDT Clock
WDT Clock Symbol
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