參數(shù)資料
型號: EM6821TQ52B
英文描述: Advanced Synchronous Rectified Buck MOSFET Drivers with Pre-POR OVP; Temperature Range: 0&degC to 70°C; Package: 8-EPSOIC
中文描述: 微控制器
文件頁數(shù): 69/69頁
文件大?。?/td> 852K
代理商: EM6821TQ52B
EM6821
10/01, Revision A/386
Copyright
2001, EM Microelectronic-Marin SA
9
www.emmicroelectronic.com
4.1 Oscillation Detection Circuit
At power on, the voltage regulator starts to follow the supply voltage and triggers the power on reset circuitry,
and thus the system reset. The CPU of the EM6821 remains in the reset state for the ‘CPU Reset Delay’, to
allow the oscillator to stabilize after power up.
The oscillator is disabled during sleep mode. So when waking up from sleep mode, the CPU of the EM6821
remains in the reset state for the CPU Reset Delay, to allow the oscillator to stabilize. During this time, the
Oscillation Detection Circuit is inhibited.
In active or standby modes, the oscillator detection circuit monitors the oscillator. If it stops for any reason, a
system reset is generated. After clock restart the CPU waits for the CPU Reset Delay before executing the first
instructions.
The oscillation detection circuitry can be inhibited with bit NoOscWD = 1 in register RegVldCntl. At power up,
and after any system reset, the function is activated.
The ‘CPU Reset Delay’ is 32768 system clocks ( Ck[16] ) long.
4.2 Reset Terminal
During active or standby modes the Reset terminal has a debouncer to reject noise. Reset must therefore be
active for at least 16 ms (system clock = 32 KHz).
When canceling sleep mode, the debouncer is not active (no clock), however, reset passes through an
analogue filter with a time constant of typical. 5s. In this case Reset pin must be high for at least 10 s to
generate a system reset.
4.3 Input Port A Reset Function
By writing the OptInpRSel1 and OptInpRSel2 registers it is possible to choose any combination of port A input
values to execute a system reset. The reset condition must be valid for at least 16ms (system clock = 32kHz) in
active and standby mode.
OPTInpRSleep selects the input port A reset function in sleep mode. If set to "1" the occurrence of the selected
combination for input port A reset will immediately trigger a system reset (no debouncer) .
Reset combination selection (InpReset) is done with registers OptInpRSel1 and OptInpRSel2.
Following formula is applicable :
InpResPA = InpResPA[0] InpResPA[1] InpResPA[2] InpResPA[3]
InpRes1PA[n] InpRes2PA[n] InpResPA[n]
00VSS
0
1
PA[n]
1
0
not PA[n]
11VDD
n = 0 to 3
i.e. ; - no reset if InpResPA[n] = VSS.
- Don't care function on a single bit with
its InpResPA[n] = VDD.
- Always Reset if InpResPA[3:0] = 'b1111
Figure 7. Input Port A Reset Structure
0
1 MUX
2
3 1 0
VSS
PA[3]
VDD
BIT
[0]
BIT
[1]
BIT
[2]
BIT
[3]
InpResPA
InpResPA[3]
InpRes2PA[3]
InpRes1PA[3]
Input Port A Reset
Bit[2] Selection
Input Port A Reset
Bit[1] Selection
Input Port A Reset
Bit[0] Selection
Input Port A Reset
Bit[3] Selection
Input
Reset
from
Port A
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