M38203M4 Datasheet, PDF (99/344 Pages) Mitsubishi Electric Semiconductor – 8-BIT SINGLE-CHIP MICROCOMPUTER

APPLICATION
2.1 I/O pins
(4) Notes in standby state
In standby state^V2 for low-power dissipation, do not make input levels of an input port and an I/O port
“undefined”, especially for I/O ports of the P-channel and the N-channel open-drain.
Pull-up (connect the port to VCC) or pull-down (connect the port to VSS) these ports through a resistor.
When determining a resistance value, note the following points:
qExternal circuit
qVariation of output levels during the ordinary operation
When using built-in pull-up or pull-down resistor as an option, note on varied current values.
qWhen setting as an input port : Fix its input level
qWhen setting as an output port : Prevent current from flowing out to external
REASON
Even when setting as an output port with its direction register, in the following state:
qP-channel......when the content of the data register (port latch) is “0”
qN-channel......when the content of the data register (port latch) is “1”
the transistor becomes the OFF state, which causes the ports to be the high-impedance state. Note
that the level becomes “undefined” depending on external circuits.
Accordingly, the potential which is input to the input buffer in a microcomputer is unstable in the state
that input levels of a input port and an I/O port are “undefined”. This may cause power source current.
V2 standby state : the stop mode by executing the STP instruction the wait mode by executing the
WIT instruction
3820 GROUP USER’S MANUAL
2–13