MC80F0204 Datasheet, PDF (98/126 Pages) List of Unclassifed Manufacturers – 8-BIT SINGLE-CHIP MICROCONTROLLERS

MC80F0104/0204
Preliminary
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.
INPUT PIN
V_DD
V_DD
internal
pull-up
i
GND
V_DD
X
Weak pull-up current flows
V_DD
O
OPEN
O
INPUT PIN
OPEN
i
V_DD
i=0
O
Very weak current flows
X
i=0
GND
O
When port is configured as an input, input level should
be closed to 0V or 5V to avoid power consumption.
Figure 19-9 Application Example of Unused Input Port
OUTPUT PIN
ON
OFF _i
GND
X
ON
OPEN
OFF
O
V_DD
ON
OFF
O
In the left case, much current flows from port to GND.
OUTPUT PIN
ON
V_DD
L
OFF
V_DD
L
OFF _i
GND
ON i=0
GND
X
O
In the left case, Tr. base current flows from port to GND.
To avoid power consumption, there should be low output
to the 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
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Mar. 2005 Ver 0.2