3825 datasheet(85/339 Pages) RENESAS

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2.1 I/O pins

APPLICATION

3825 GROUP USER’S MANUAL

2–13

(4) Notes in standby state

In standby stateV2 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

3825 Datasheet(PDF) 85 Page - Renesas Technology Corp