SM1124 Datasheet, PDF (7/10 Pages) Nippon Precision Circuits Inc – Multimelody IC for Pagers

SM1124 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
represents either a note (sound pitch and length) or a
rest.
Note length (including rests)
Eight rhythm values for notes (rests) can be
programmed. Also, 2 or more notes can be
programmed as tied notes using a tie.
0
1
2
3
4
5
6
7
Note
Rest
3
3
3
3
Pitch and scale
The SM1124 performs 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 external reference clock
frequency, as shown in the frequency on the
following page.
The frequency variation from the input frequency is
the sum of the relative error, shown in the frequency
table, plus the pitch error.
(Ex) 38.4 kHz system, A4 note
Relative error: 8.99 cent
Pitch error: −3.58 cent
Total: +5.41 cent
Error calculation method:
1200
×
log₂
----O-----u---t-p---u---t---f--r--e---q---u---e---n---c--y------
Reference frequency
=
1200
×
-l-o---g---¹---⁰---R--------Oe------f---u-e-----t-r--p--e----un------tc------ef----r----fe----r--q--e----u--q----e--u---n---e---c--n---y---c-----y----
log ₁₀ 2
≈ 3986.3 × log_{10R----Oe---f--ue---tr-p-e--un---tc---ef--r--fe--r-q-e--u-q--e-u--n-e--c-n-y--c--y--}
≈
3986.3
×
log ₁₀
4---4---1---.--3---7---9-
440.000
≈ 5.41 cent
NIPPON PRECISION CIRCUITS—7