¡ Semiconductor

MSM6786

11/17

FEDL6786-03

R0

R1

R2

R3

R4

Scan Start Command Write

or Key Status Changed

Data Read

Data Read

Data Read

Scan Stop Command

Write

INT

Keyscan

Keyscan starts when the key state is changed or when the "Keyscan Start" command is written.

Scan continues until the "Keyscan Stop" command is written. (When powered on, the power-

ON reset sets at scan stop state.)

interrupt flag, which is dependent on switching conditions of keys. The INT signal is reset when

either the LOAD pulse is input after key data is output, when the "Keyscan Stop" command is

set, or when a reset signal is applied.

Notes : 1. A recognition error may occur if 3 or more key switches are pressed at the same time.

(A switch that was not pressed is recognized as being pressed.) To properly

recognize 3 or more key switches as being pressed at the same time, serially insert

diodes at each switch. In order not to recognize 3 or more key switches as being

pressed at the same time, a possible approach is to program the software so that the

read data will be ignored when there are 3 or more ones in the data.

The device recognizes simultaneous pressing of 2 key switches. However, take Note

2 into consideration.

2. A change of key state is detected as a change in column input (C0 - C5). Therefore

even if multiple switches connected to the same column are pressed at the same time,

nothing will be detected as a change.