CS4218 Datasheet, PDF (15/44 Pages) Cirrus Logic – 16-Bit Stereo Audio Codec

CS4218
first, 2’s complement format. Sub-frame bit as-
signments are shown in Figure 13. Control data
bits all reset to zero.
the master CLKIN is multiplied internally by 16,
so a 16xFs input clock must be provided.
CS4218 SERIAL INTERFACE MODES
The CS4218 has three serial port modes, selected
by the SMODE1, SMODE2 and SMODE3 pins.
In all modes, CLKIN, SCLK and SSYNC must
be derived from the same clock source. SM3
was designed as an easy interface to general pur-
pose DSPs and provides features such as master
and slave sub-modes and variable frame sizes.
SM4 is similar to SM3 but splits the audio data
from the control data thereby reducing the audio
serial bus bandwidth by half. The control data is
transmitted through a control serial port in SM4.
SM5 is compatible with the I²S serial data proto-
col.
Table 2 lists the three serial port modes avail-
able, along with some of the differences between
modes. The first three columns in Table 2 select
the serial mode. The "SCLK Bit Center" column
indicates whether SCLK is rising or falling in
the center of a bit period. The "Sub-frame
Width" column indicates how many bits are in
an individual codec’s sub-frame. In SM3 and
SM4, the number of bits per frame is program-
mable. In all modes, SCLK and SSYNC must be
synchronous to the master clock. The last col-
umn in Table 2 lists the master frequencies used
by the codec. In the SM3 Multiplier sub-modes,
SERIAL MODE 3, (SM3)
Serial Mode 3, Master and Slave sub-modes are
enabled by setting SMODE3 = 0, SMODE2 = 1
and SMODE1 = 0. SM3 Multiplier Sub-Modes
are enabled by setting SMODE 3 = 0, SMODE
2 = 0, and SMODE 1 = 0. Serial Mode 3 is de-
signed to interface easily to DSPs.
Figure 11 illustrates the serial data in, SDIN,
sub-frame for all SM3 sub-modes. Figure 12
also illustrates the serial data out, SDOUT, sub-
frame for all SM3 sub-modes. Figure 13 shows
sub-frame bit definitions.
In SM3 master sub-modes, MF5:DO2 is a gen-
eral purpose output and MF6:DI2 is a general
purpose input. The other six multifunction pins
are used to select sub-modes under SM3. In
SM3 slave sub-modes, MF3:F3 is configured as
an additional general purpose input.
SM3 is divided into four sub-modes, Master
(SM3-M), Slave (SM3-S), Multiplier Master
(SM3-MM), and Multiplier Slave (SM3-MS).
SM3-M and SM3-S are identical to the CS4216
SM3 Master and Slave sub-modes, respectively.
In SM3-M and SM3-MM sub-modes, the
CS4218 generates SSYNC and SCLK, while in
SM3-S and SM3-MS sub-modes SSYNC and
SMODE PINS Serial SCLK Bit Sub-frame Bits per
SCLK &
3 2 1 Mode Center
Width Frame (BPF) SSYNC
Master
Frequency
0 0 0 SM3* Falling
64 bits 64/128/256 Master/Slave CLKIN = 16xFs
0 0 1 SM5
Rising
64 bits
64
Master
CLKIN = 256xFs
0 1 0 SM3
Falling
64 bits
64/128/256 Master/Slave CLKIN or SCLK = 256×Fs
011
Factory Test mode
1 x x SM4
Falling
32 bits^†
32/64/128^† Master/Slave CLKIN = 256×Fs
†_{Contains audio data only. Control information is entered through a separate serial port.}
* SM3 Multiplier sub-modes.
Table 2. Serial Port Modes
DS135F1
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