SM1125_06 Datasheet, PDF (8/13 Pages) Nippon Precision Circuits Inc – Multimelody IC for Pagers

SM1125 series
Musical Specifications
Maximum program steps
The mask for the built-in ROM can be programmed with up to a maximum of 512 steps, where each step repre-
sents either a note (sound pitch and length) or a rest.
Note length (including rests)
Eight rhythm values for notes and rests can be programmed. Also, 2 or more notes can be musically tied.
Table 3. Rhythm values
0
1
2
3
4
5
6
7
Note
Rest
Pitch and scale
SM1125 series devices perform uniform interval length processing to reduce the error at high pitches. This
maintains the relative phase when the frequency varies from the input value.
The pitch varies with the clock frequency, as shown in the frequency listing in table 4.
The frequency variation from the input frequency is the sum of the relative error, shown in the frequency table,
plus the pitch error.
(Ex) 38.4kHz system, A4 note
Relative error: 8.99 cent
Pitch error: −3.58 cent
Total: +5.41 cent
Error calculation:
1200
×
log₂
Output frequency
Reference frequency
=
1200
×
log₁₀
Output frequency
Reference frequency
log₁₀2
≈
3986.3
×
log₁₀
Output frequency
Reference frequency
≈ 3986.3 × log₁₀
441.379
440.000
≈ 5.41 cent
SEIKO NPC CORPORATION —8