SM1125_06 Datasheet, PDF (5/13 Pages) Nippon Precision Circuits Inc – Multimelody IC for Pagers

SM1125 series
FUNCTIONAL DESCRIPTION
Control Functions
Reference clock
SM1125 series devices are available in external clock input versions and built-in RC oscillator versions, set by
master-slice option. In the case of the built-in RC oscillator option, an external resistor and capacitor is
required for the oscillator function.
SM1125 series can operate at 12 selectable reference clock frequencies. All melodies playback at the fixed
speed set by the reference clock frequency. External clock input versions operate at one of 12 selectable clock
frequencies, as shown in table 1. Built-in RC oscillator versions operate at one of 4 selectable oscillator fre-
quencies—32.768kHz, 37.5kHz, 38.4kHz (standard frequency) and 48.0kHz.
Table 1. Reference clock frequencies
Frequency
system
32.768kHz
37.5kHz
38.4kHz
48.0kHz
Selectable frequencies
32.768kHz
37.5kHz
38.4kHz
48.0kHz
65.536kHz
75.0kHz
76.8kHz
96.0kHz
131.072kHz
150.0kHz
153.6kHz
192.0kHz
In external clock input versions, the external reference clock input is used during playback mode only and is
otherwise ignored. If a clock signal is input when not in playback mode (when ST is LOW), the gate circuit
switches to cutoff the external reference clock signal from entering the device, preventing unwanted current
flow.
In built-in RC oscillator versions, the oscillator is stopped when not in playback mode (when ST is LOW), pre-
venting unwanted current flow.
ST
OSC
Figure 1. External clock input version: Input during playback mode only
ST
OSC
Figure 2. External clock input version: Input during non-playback mode
ST
OSC
CR Oscillator
Figure 3. Built-in RC oscillator version
SEIKO NPC CORPORATION —5