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| 型号： | MCZ33812EK |
| 厂商： | Freescale Semiconductor |
| 文件页数： | 18/25页 |
| 文件大小： | 0K |
| 描述： | IC DVR IGNITION/INJECTOR 32-SOIC |
| 标准包装： | 42 |
| 应用： | 自动 |
| 电流 - 电源： | 10mA |
| 电源电压： | 4.7 V ~ 36 V |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 32-BSOP（0.295"，7.50mm 宽）裸露焊盘 |
| 供应商设备封装： | 32-SOICW 裸露焊盘 |
| 包装： | 管件 |
FUNCTIONAL DEVICE OPERATION
WATCHDOG TIMER OPERATION
WATCHDOG TIMER OPERATION
The purpose of the watchdog timer is to provide a RESET
to the MCU whenever the MCU is locked up in a loop or
otherwise hung up, perhaps by executing erroneous code,
such as a HALT instruction. The watchdog timer is initialized
by a power on RESET or a RESET that occurs after a fault
such as an under-voltage event on VCC.
Whenever the watchdog timer is refreshed, it is always
reloaded with the value WD RELOAD which initially has a value
of WD MAX seconds. Whenever a RESET occurs, the
WD RELOAD value is set to WD MAX seconds and the watchdog
timer is re-loaded with this value. When the RESET pulse
will be inhibited from issuing a RESET to the MCU, while the
line is held in this state. This “watchdog Inhibited” state
should only be used during software testing and development
to avoid being concerned about an inadvertent watchdog
RESET.
Watchdog Timing Diagrams
Watchdog Loaded with WD MAX
returns high, and, if the WDRFSH line is low, the watchdog
timer starts counting. If the watchdog timer reaches the
WD MAX value before the next rising edge on the WDRFSH
line, the watchdog circuit will generate a RESET pulse to the
MCU and reload itself with the maximum time value of
WD RELOAD , which will have been set back to WD MAX
seconds.
5
4
3
2
1
0
WDRFSH
Holding WDRFSH high will trigger RESET every WD MAX time
Time
In normal operation, the MCU will issue a WDRFSH pulse,
5
Watchdog timer
& WD RELOAD = WD MAX
PW A < WD LOAD
PW B > WD LOAD
WDRFSH
periodically, which re-loads the watchdog timer with the
WD RELOAD value and starts the counting again, thus avoiding
a watchdog timer generated RESET pulse. When the
watchdog timer is refreshed by a WDRFSH pulse, before the
watchdog timer reaches the programmed value, the refresh
will prevent a RESET pulse from being issued to the MCU.
Loading the Watchdog Timer and WD RELOAD
Aside from the RESET case, which always loads the
WD RELOAD value and the watchdog timer with the maximum
time value, WD MAX , there is an additional way that the
watchdog timer and the value WD RELOAD can be re-loaded.
During initialization, if the WDRFSH pulse width is greater
than WD LOAD , both the watchdog timer and the value
WD RELOAD will be loaded with a timer count value,
corresponding to the width of the pulse present on the
WDRFSH input. Once this value is set, no further setting of
the WD LOAD value is possible until a RESET is performed.
Once the WDRFSH input goes low, the watchdog timer will
begin incrementing again, counting up to the new value that
has been loaded into the reload register. The watchdog must
be refreshed by another pulse on the WDRFSH line, before
the watchdog timer counts up to the reload value, or else a
RESET pulse will be generated and sent to the MCU.
If the WDRFSH line is ever kept high for longer than
WD RELOAD seconds, the watchdog will issue an immediate
RESET to the MCU. Upon receiving a RESET input from the
33812, the MCU should always be programmed to bring the
WDRFSH line low to avoid being locked in a “deadly
embrace” condition where the MCU and 33812 alternate
back and forth between the RESET and Normal states.
Disabling the Watchdog Timer
If the WD_INH line is pulled high through a pull-up resistor
Voltage
RESET
4
3
2
1
0
RESET loads the watchdog timer and WD RELOAD with WD MAX Time
Voltage
5
4
3
2
1 WDRFSH
0
Time
Refresh pulses, PW A , on WDRFSH load the Watchdog timer with the
WD RELOAD
Voltage
5
4
3
2
1
0
Time
During initialization, for the first WDRFSH pulse only, PW B , that is greater
than WD LOAD but less than WD MAX , the Watchdog timer and WD RELOAD
value will be loaded with a time value corresponding to the width of that
pulse, PW B . All pulses on the WDRFSH line width less than WD RELOAD, will
result in the Watchdog timer being reloaded with the time value correspond-
ing to PW B . This programmability is only allowed once per RESET.
of 10 K or less, (i.e. not tied to ground), the watchdog timer
33812
Analog Integrated Circuit Device Data
18
Freescale Semiconductor
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相关代理商/技术参数 |
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| MCZ33812EK/R2 | 制造商:FREESCALE 制造商全称:Freescale Semiconductor, Inc 功能描述:Multifunctional Ignition and Injector Driver |
| MCZ33812EKR2 | 功能描述:马达/运动/点火控制器和驱动器 MULTIFUNC IGN, INJ DRVR RoHS:否 制造商:STMicroelectronics 产品:Stepper Motor Controllers / Drivers 类型:2 Phase Stepper Motor Driver 工作电源电压:8 V to 45 V 电源电流:0.5 mA 工作温度:- 25 C to + 125 C 安装风格:SMD/SMT 封装 / 箱体:HTSSOP-28 封装:Tube |
| MCZ33879AEK | 功能描述:电源开关 IC - 配电 CONFIG OCTAL SERIAL SW RoHS:否 制造商:Exar 输出端数量:1 开启电阻（最大值）:85 mOhms 开启时间（最大值）:400 us 关闭时间（最大值）:20 us 工作电源电压:3.2 V to 6.5 V 电源电流（最大值）: 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:SOT-23-5 |
| MCZ33879AEK/R2 | 制造商:FREESCALE 制造商全称:Freescale Semiconductor, Inc 功能描述:Configurable Octal Serial Switch with Open Load Detect Current Disable |
| MCZ33879AEKR2 | 功能描述:电源开关 IC - 配电 CONFIG OCTAL SERIAL SW RoHS:否 制造商:Exar 输出端数量:1 开启电阻（最大值）:85 mOhms 开启时间（最大值）:400 us 关闭时间（最大值）:20 us 工作电源电压:3.2 V to 6.5 V 电源电流（最大值）: 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:SOT-23-5 |
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