SM1124 Series

NIPPON PRECISION CIRCUITS—7

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.

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:

01234567

3

3

Rest

Note

3

3

1200

log

2

Output frequency

Reference frequency

-------------------------------------------------

×

1200

log

10

Output frequency

Reference frequency

-------------------------------------------------

log

---------------------------------------------------------------

×

=

3986.3

log

10

Output frequency

Reference frequency

-------------------------------------------------

×

≈

3986.3

log

10

441.379

440.000

-------------------

×

≈

5.41 cent

≈