GMS81C2020 Datasheet, PDF (76/92 Pages) Hynix Semiconductor – CMOS Single-Chip 8-Bit Microcontroller with A/D Converter & VFD Driver

GMS81C2020/GMS81C2120
Hyundai Micro Electro nics
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.
Note: In the STOP operation, the power dissipation asso-
ciated with the oscillator and the internal hardware
is lowered; however, the power dissipation associat-
ed 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 voltage level (V_DD/V_SS);
however, when the input level becomes higher 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 that current flow through port
doesn't exist.
First conseider the 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 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 unfirmed voltage level
(not V_SSor 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 re-
sistor 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
* Pull-up is Metal Option
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 21-2 Application Example of Unused Input Port
76
preliminary
Nov. 1999 Ver 0.0