GMS81C7216 Datasheet, PDF (83/121 Pages) List of Unclassifed Manufacturers – 8-BIT SINGLE-CHIP MICROCONTROLLERS

GMS81C7208/7216
It should be set properly that current flow through port doesn't ex-
ist.
First consider the setting to input mode. Be sure that there is no
current flow after considering its relationship with external cir-
cuit. In input mode, the pin impedance viewing from external
MCU is very high that the current doesn’t flow.
But input voltage level should be V_SS or V_DD. Be careful that if
unspecified voltage, i.e. if un-firmed voltage level (not V_SS or
V_DD) is applied to input pin, there can be little current (max. 1mA
at around 2V) flow.
If it is not appropriate to set as an input mode, then set to output
mode considering there is no current flow. Setting to High or Low
is decided considering its relationship with external circuit. For
example, if there is external pull-up resistor then it is set to output
mode, i.e. to High, and if there is external pull-down register, it is
set to low.
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 configure as an input, input level should
be closed to 0V or 5V to avoid power consumption.
Figure 20-6 Application Example of Unused Input Port
OUTPUT PIN
ON
OFF _i
GND
X
ON
OPEN
OFF
O
V_DD
ON
O ^OFF
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 20-7 Application Example of Unused Output Port
FEB. 2005 Ver 1.04
79