em6522 EM Microelectronic, em6522 Datasheet - Page 10

• Manufacturer Part Number: em6522
• Description: Mfp Version Of Em6622 Ultra Low Power Microcontroller With 4x32 Lcd Driver
• Manufacturer: EM Microelectronic

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 EM6522 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 EM6522
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. 5µs. In this case Reset pin must be high for at least 10 µs 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]
n = 0 to 3
i.e. ; - no reset if InpResPA[n] = V
Copyright © 2005, EM Microelectronic-Marin SA
InpRes1PA[n] InpRes2PA[n] InpResPA[n]
0
0
1
1
- Don't care function on a single bit with
- Always Reset if InpResPA[3:0] = 'b1111
its InpResPA[n] = V
R
0
1
0
1
DD
.
V
PA[n]
not PA[n]
V
SS
SS
DD
.
Figure 7. Input Port A Reset Structure
BIT
BIT
BIT
Input Port A Reset
Bit[3] Selection
BIT
[0]
[1]
[3]
[2]
InpRes1PA[3]
InpRes2PA[3]
10
Input Port A Reset
Bit[0] Selection
Input Port A Reset
Bit[1] Selection
Input Port A Reset
Bit[2] Selection
V
PA[3]
PA[3]
V
SS
DD
0
1 MUX
2
3 1 0
InpResPA[3]
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EM6522
InpResPA
Input
Reset
from
Port A