16 SOUND GENERATOR (SNDA)
16-10
Seiko Epson Corporation
S1C17M20/M21/M22/M23/M24/M25
TECHNICAL MANUAL (Rev. 1.0)
Bits 6–4
CLKDIV[2:0]
These bits select the division ratio of the SNDA operating clock.
Bits 3–2
Reserved
Bits 1–0
CLKSRC[1:0]
These bits select the clock source of SNDA.
Table 16.6.1 Clock Source and Division Ratio Settings
SNDCLK.
CLKDIV[2:0] bits
SNDCLK.CLKSRC[1:0] bits
0x0
0x1
0x2
0x3
IOSC
OSC1
OSC3
EXOSC
0x7
Reserved
1/1
Reserved
1/1
0x6
0x5
1/128
1/128
0x4
1/64
1/64
0x3
1/32
1/32
0x2
1/16
1/16
0x1
1/8
1/8
0x0
1/4
1/4
(Note) The oscillation circuits/external input that are not supported in this IC cannot be
selected as the clock source.
Note: The SNDCLK register settings can be altered only when the SNDCTL.MODEN bit = 0.
SNDA Select Register
Register name
Bit
Bit name
Initial
Reset
R/W
Remarks
SNDSEL
15–12 –
0x0
–
R
–
11–8 STIM[3:0]
0x0
H0
R/W
7–3 –
0x00
–
R
2
SINV
0
H0
R/W
1–0 MOSEL[1:0]
0x0
H0
R/W
Bits 15–12 Reserved
Bits 11–8 STIM[3:0]
These bits select a tempo (when melody mode is selected) or a one-shot buzzer output duration (when
one-shot buzzer mode is selected).
Table 16.6.2 Tempo/One-shot Buzzer Output Duration Selections (when f
CLK_SNDA
= 32,768 Hz)
SNDSEL.
STIM[3:0] bits
Tempo
(= Quarter note/minute)
One-shot buzzer output
duration [ms]
0xf
30
250.0
0xe
32
234.4
0xd
34.3
218.8
0xc
36.9
203.1
0xb
40
187.5
0xa
43.6
171.9
0x9
48
156.3
0x8
53.3
140.6
0x7
60
125.0
0x6
68.6
109.4
0x5
80
93.8
0x4
96
78.1
0x3
120
62.5
0x2
160
46.9
0x1
240
31.3
0x0
480
15.6
Note
: Be sure to avoid altering these bits when SNDINTF.SBSY bit = 1.
Bits 7–3
Reserved