CS4218 Datasheet, PDF (23/44 Pages) Cirrus Logic – 16-Bit Stereo Audio Codec

CS4218
In Master sub-mode, multifunction pins MF6:F1,
MF7:F2, and MF8:F3 select the sample fre-
quency as shown in Table 7. This table indicates
how to obtain standard audio sample frequencies
given one of two CLKIN frequencies:
12.288 MHz or 11.2896 MHz. Other CLKIN fre-
quencies may be used with the corresponding
sample frequencies being CLKIN/N. A change in
sample rate automatically initiates a calibration
cycle.
MF6:
F1
0
0
0
0
1
1
1
1
MF7:
F2
0
0
1
1
0
0
1
1
MF8: N
F3
0 256
1 384
0 512
1 640
0 768
1 1024
0 1280
1 1536
Fs (kHz)
with CLKIN
12.288 11.2896
MHz
MHz
48.00 44.10
32.00 29.40
24.00 22.05
19.20 17.64
16.00 14.70
12.00 11.025
9.60
8.82
8.00
7.35
Table 7. SM4-Master, Fs Select
Slave Sub-Mode (SM4)
In SM4, Slave sub-mode is selected by setting
SMODE1,SMODE2 = 01. This mode configures
SSYNC and SCLK as inputs to the CS4218.
These two signals must be externally derived
from CLKIN. Since the CS4218 has no control
over the phase relationship of SSYNC and
SCLK to CLKIN, the noise performance in
Slave sub-mode may be slightly worse than
when using Master sub-mode. The CS4218 inter-
nally sets the sample frequency by sensing the
ratio of SCLK to CLKIN; therefore, for a given
CLKIN frequency, the sample frequency is se-
lected by changing the SCLK frequency. A
change in sample rate automatically initiates a
calibration cycle. Table 9 shows the sample rates
generated with two example clocks.
SM4-Slave allows up to four codecs to occupy
the same audio serial port. Table 8 lists the pin
configurations required to set the serial audio
port up for 32, 64, or 128 bits-per-frame (BPF).
Since each codec requires one sub-frame of
32 bits, 64 bits-per-frame allows up to two
codecs to occupy the same audio serial port, and
128 bits-per-frame allows up to four codecs to
occupy the same audio serial port. When set up
for more than one codec on the bus, other pins
are needed to select the particular time slot (TS)
associated with each codec. MF8:SFS2 selects
the time slot when in 64 BPF mode, and
MF8:SFS2 and MF7:SFS1 select one of four
time slots when in 128 bits-per-frame mode. Ta-
ble 8 lists the decoding for time slot selection.
MF6: MF7: MF8:
F1 SFS1 SFS2
0
0
0
0
0
1
0
1
0
0
1
1
1
0
0
1
1
0
1
0
1
1
1
1
Bits Per
Frame
(BPF)
Time
Slot
(TS)
32
1
Reserved
64
1
64
2
128
1
128
2
128
3
128
4
Table 8. SM4-Slave, Audio Port BPF & TS Select
SCLK to CLKIN Ratio Fs (kHz) Fs (kHz)
BPF BPF BPF with CLKIN with CLKIN
128 64 32 12.288 MHz 11.2896 MHz
2
4
8
48.00
44.10
3
6
12
32.00
29.40
4
8
16
24.00
22.05
5
10 20
19.20
17.64
6
12 24
16.00
14.70
8
16 32
12.00
11.025
10 20 40
9.60
8.82
12 24 48
8.00
7.35
Table 9. SM4-Slave, Fs Select.
DS135F1
23