Cirrus Logic CS4205 - Manual (Page 13)

CS4205
DS489PP4 13
2. GENERAL DESCRIPTION
The CS4205 is a mixed-signal serial audio codec
compliant with the Intel
® Audio Codec ’97 Specifi-
cation, revision 2.1 [6] (referred to as AC ’97). It is
designed to be paired with a digital controller, typ-
ically located on the PCI bus or integrated within
the system core logic chip set. The controller is re-
sponsible for all communications between the
CS4205 and the remainder of the system. The
CS4205 contains two distinct functional sections:
digital and analog. The digital section includes the
AC-link interface, S/PDIF interface, serial data
port, GPIO, signal processing engine, ZV Port,
power management support, and Sample Rate Con-
verters (SRCs). The analog section includes the an-
alog input multiplexer (mux), stereo input mixer,
stereo output mixer, mono output mixer, stereo An-
alog-to-Digital Converters (ADCs), stereo Digi-
tal-to-Analog Converters (DACs), dedicated mono
microphone ADC, and their associated volume
controls.
2.1 AC-Link
All communication with the CS4205 is established
with a 5-wire digital interface to the controller
called the AC-link. This interface is shown in
Figure 7. All clocking for the serial communication
is synchronous to the BIT_CLK signal. BIT_CLK
is generated by the primary audio codec and is used
to clock the controller and any secondary audio co-
decs. Both input and output AC-link audio frames
are organized as a sequence of 256 serial bits form-
ing 13 groups referred to as ‘slots’. During each au-
dio frame, data is passed bi-directionally between
the CS4205 and the controller. The input frame is
driven from the CS4205 on the SDATA_IN line.
The output frame is driven from the controller on
the SDATA_OUT line. The controller is also re-
sponsible for issuing reset commands via the RE-
SET# signal. Following a Cold Reset, the CS4205
is responsible for notifying the controller that it is
ready for operation after synchronizing its internal
functions. The CS4205 AC-link signals must use
the same digital supply voltage as the controller, ei-
ther +5 V or +3.3 V. See Section 4, AC-Link Frame
Definition, for detailed AC-link information.
CODEC SYNC
BIT_CLK
SDATA_OUT
SDATA_IN
RESET#
Digital AC'97
Controller
AC'97
Figure 7. AC-link Connections