sm1125abv Nippon Precision Circuits Inc, (NPC), sm1125abv Datasheet - Page 5

• Manufacturer Part Number: sm1125abv
• Description: Multimelody Pagers
• Manufacturer: Nippon Precision Circuits Inc, (NPC)

FUNCTIONAL DESCRIPTION
Control Functions
Reference clock
SM1125ABV has built-in RC oscillator circuit (oscillation frequency: 38.4kHz typ).
Power-saving function
The built-in RC oscillator is stopped when not in playback mode (when ST is LOW), preventing unwanted cur-
rent flow.
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 1.
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
Table 1. Serial data melody select
B3
L
L
L
L
L
L
OSC
ST
B2
H
H
L
L
L
L
B1
H
H
L
L
L
L
MTO
MTO
Pin SC should be LOW when either a LOW-to-HIGH or HIGH-to-LOW transition occurs on pin ST.
SC
SC
ST
ST
SI
SI
B0
Melody plays repeatedly when ST is HIGH, and stops immediately when ST goes LOW.
H
H
H
L
L
L
Invalid
Data
? ?
B3 B2 B1 B0
L → H
L → H
L → H
L → H
L → H
L → H
#n1 Data
ST
Valid
Data
Figure 1. Oscillator circuit operation
Figure 3. Melody repetition timing
Figure 2. Serial data input timing
#n1 Play
2nd melody
3rd melody
4th melody
5th melody
6th melody
1st melody
Melody
#n1 Play
SM1125ABV
RC Oscillator
#n1 Play
B3
H
H
H
H
L
L
?
#n2 Data
Invalid
Data
?
? ?
B2
H
H
L
L
L
L
#n2 Play
B1
H
H
H
H
L
L
SEIKO NPC CORPORATION —5
B0
H
H
H
L
L
L
L → H
L → H
L → H
L → H
L → H
L → H
ST
10th melody
11th melody
12th melody
7th melody
8th melody
9th melody
Melody