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MC80F0104/0204
Preliminary
94
Mar. 2005 Ver 0.2
19.4 Minimizing Current Consumption
The Stop mode is designed to reduce power consumption.
To minimize current drawn during Stop mode, the user
should turn-off output drivers that are sourcing or sinking
current, if it is practical.
Figure 19-9 Application Example of Unused Input Port
Figure 19-10 Application Example of Unused Output Port
Note:
In the STOP operation, the power dissipation associated
with the oscillator and the internal hardware is lowered; however,
the power dissipation associated with the pin interface (depending
on the external circuitry and program) is not directly determined by
the hardware operation of the STOP feature. This point should be
little current flows when the input level is stable at the power volt-
age level (V
DD
/V
SS
); however, when the input level becomes high-
er than the power voltage level (by approximately 0.3V), a current
begins to flow. Therefore, if cutting off the output transistor at an I/
O port puts the pin signal into the high-impedance state, a current
flow across the ports input transistor, requiring it to fix the level by
pull-up or other means.
It should be set properly in order that current flow through
port doesn't exist.
First consider the port setting to input mode. Be sure that
there is no current flow after considering its relationship
with external circuit. In input mode, the pin impedance
INPUT PIN
V
DD
GND
i
V
DD
X
Weak pull-up current flows
V
DD
internal
pull-up
INPUT PIN
i
V
DD
X
Very weak current flows
V
DD
O
O
OPEN
OPEN
i=0
O
i=0
O
GND
When port is configured as an input, input level should
be closed to 0V or 5V to avoid power consumption.
OUTPUT PIN
GND
i
In the left case, much current flows from port to GND.
X
ON
OFF
OUTPUT PIN
GND
i
In the left case, Tr. base current flows from port to GND.
i=0
X
OFF
ON
V
DD
L
ON
OFF
OPEN
GND
V
DD
L
ON
OFF
To avoid power consumption, there should be low output
ON
OFF
O
O
V
DD
O
to the port .
Содержание MC80F0104
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