SM1350 series

NIPPON PRECISION CIRCUITS—8

S0 to S3 chattering prevention function

In binary select mode, S0 to S3 are sampled in sync

with the 15.26 Hz clock during level-hold melody

output. The chatter prevention function compares the

data sampled 65.5 ms after a data transition on S0 to

S3 with the data sampled 65.5 ms before the data

transition. If the 2 data samples are the same, then

the data transition is considered invalid. However, if

they are the not the same indicating a true transition

has occurred, melody output stops and only restarts

again after 2 consecutive identical melody select data

samples occur.

Note that except for the “Select change retrigger

[No]” master slice option and binary select mode

with level hold output, the S0 to S3 chattering

prevention circuit is disabled.

Initialization

When power on and ICN goes LOW, all pins and internal states are initialized to the states shown below. ICN

initialization has priority over all other inputs.

s

Output pins

• SP, SPN

Open

• MSB, MSBN

•CT

• BUSYN

s

Serial melody counter

Reset to first melody (S0 to S3 all 1)

s

Oscillator circuit

Stopped

Note: Refer to the "TIMING DIAGRAMS" section to confirm melody timing specifics.

Figure 3. S0 to S3 chattering prevention timing

15.26Hz

S0 to S3

#N

#M

#S

65.5

ms

65.5

ms

65.5

ms

65.5

ms

65.5

ms

65.5

ms

#N

#N

#M

#S

Melody

Output