M38B53M4-059FP datasheet(269/355 Pages) MITSUBISHI

269 / 355 page

38B5 Group User’s Manual

3-21

APPENDIX

3.3 Notes on use

(2)

N-channel open-drain port

P40–P42, P45, P46, P60 of N-channel open-drain output ports have built-in hysteresis circuit for input.

In standby state for low-power dissipation, do not make these pins floating state.

q Reason

When power sources for pull-up of these pins are cut off in standby state, these ports become

floating. Accordingly, a current may flow from Vcc to Vss through built-in hysteresis circuit.

(3)

Modifying output data with bit managing instruction

When the port latch of an I/O port is modified with the bit managing instruction*2, the value of the

unspecified bit may be changed.

q Reason

The bit managing instructions are read-modify-write form instructions for reading and writing data

by a byte unit. Accordingly, when these instructions are executed on a bit of the port latch of an

I/O port, the following is executed to all bits of the port latch.

• As for a bit which is set for an input port :

The pin state is read in the CPU, and is written to this bit after bit managing.

• As for a bit which is set for an output port :

The bit value of the port latch is read in the CPU, and is written to this bit after bit managing.

Note the following :

• Even when a port which is set as an output port is changed for an input port, its port latch holds

the output data.

• As for a bit of the port latch which is set for an input port, its value may be changed even when

not specified with a bit managing instruction in case where the pin state differs from its port latch

contents.

*2 bit managing instructions : SEB, and CLB instructions

M38B53M4-059FP Datasheet(PDF) 269 Page - Mitsubishi Electric Semiconductor