ST10R272L - POWER REDUCTION MODES
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•
For the 5 volt device, The oscillator needs at least 27.5 ms to stabilize (T
DIS
= 0.0275 s),
V
TH
is 2.5 V, and I is 200µA. The minimum capacitor value for C is then 2.2
µF
When using an external oscillator, the
value of C can be very small for fast recovery from Power Down mode. For example, a 1
nF capacitor will produce a discharge time of 12.5 µs.
•
For the 3.3 volt device, The oscillator needs at least 27.5 ms to stabilize (T
DIS
= 0.0275
s), V
TH
is 2.0V, and I is 200µA. The minimum capacitor value for C is then 1.83
µF
When using an external oscillator, the
value of C can be very small for fast recovery from Power Down mode. For example, a 1
nF capacitor will produce a discharge time of 6.5µs.
The external R resistor value must not interfere with the discharge current. A value between
200 kohms and 1 Mohms should be adequate.
Note
The RC circuit is also used for asynchronous Power Up reset.
17.3
Status of output pins during idle and power down mode
During Idle Mode the CPU clocks are turned off, while all peripherals continue their
operation as normal. Therefore, all ports pins which are configured as general purpose
output pins, output the last data value which was written to their port output latches. If the
alternate output function of a port pin is used by a peripheral, the state of the pin is
determined by the operation of the peripheral.
Port pins which are used for bus control functions, go into that state which represents the
inactive state of the respective function (e.g. WR), or to a defined state which is based on the
last bus access (e.g. BHE). Port pins which are used as external address/data-bus, hold the
address/data which was output during the last external memory access before entry into Idle
Mode under the following conditions:
•
P0H outputs the high-byte of the last address if a multiplexed bus mode with 8-bit data
bus is used, otherwise P0H is floating. P0L always floats in Idle Mode.
•
Port1 outputs the lower 16 bits of the last address if a demultiplexed bus mode is used,
otherwise the output pins of Port1 represent the port latch data.
•
Port 4 outputs the segment address for the last access on those pins that were selected
during reset, otherwise the output pins of Port 4 represent the port latch data.
During Power Down mode the oscillator, CPU and peripheral clocks are turned off. As for
Idle Mode, all port pins which are configured as general purpose output pins, output the last
data-value which was written to their port output latches.
When the alternate output function of a port pin is used by a peripheral, the state of this pin
is determined by the last action of the peripheral before the clocks were switched off.
C
0,0275
200
5
2,5
–
(
)
⁄
×
2,2
µ
F
=
=
C
0,0275
200
3,3
2,0
–
(
)
⁄
×
4,23
µ
F
=
=
