SM1125 series

SEIKO NPC CORPORATION —6

Playback control

The ST pin controls the start of playback. While ST is HIGH, the melody is played repeatedly, and when ST

goes LOW, playback stops. Melodies are selected by input serial data on pins SI and SC, as shown in table 2.

The final 4 serial data bits in any input data string form the valid selection data, and this data is retained even

after playback. If serial data is input during playback, the data is ignored and playback continues.

Serial data selection

Pin SC should be LOW when either a LOW-to-HIGH or HIGH-to-LOW transition occurs on pin ST.

Figure 4. Serial data input timing

Table 2. Serial data melody select

B3

B2

B1

B0

ST

Melody

B3

B2

B1

B0

ST

Melody

LLLL

L

→ H

1st melody

H

L

L

L

L

→ H

9th melody

LLL

H

L

→ H

2nd melody

H

L

L

H

L

→ H

10th melody

L

LHL

L

→ H

3rd melody

HLHL

L

→ H

11th melody

LL

H

H

L

→ H

4th melody

H

L

H

H

L

→ H

12th melody

LHL

L

L

→ H

5th melody

H

H

L

L

L

→ H

13th melody

LHLH

L

→ H

6th melody

H

H

L

H

L

→ H

14th melody

LH

HL

L

→ H

7th melody

H

H

H

L

L

→ H

15th melody

L

HHH

L

→ H

8th melody

HHHH

L

→ H

16th melody

Melody plays repeatedly when ST is HIGH, and stops immediately when ST goes LOW.

Figure 5. Melody repetition timing

SI

SC

ST

MTO

?

?? ?

Invalid

Data

Valid

Data

Invalid

Data

SI

SC

ST

MTO

#n1 Data

#n2 Data

#n1 Play

#n1 Play

#n1 Play

#n2 Play