CS4218 Datasheet, PDF (40/44 Pages) Cirrus Logic – 16-Bit Stereo Audio Codec

CS4218
Appendix B: Applications of SM4
Figure B1 illustrates one method of using Serial Mode 4 wherein a DSP controls the audio serial port
and a microcontroller controls the control port. Each controller is run independently and the micro
updates the control information only when needed, or when an interrupt from the CS4218 occurs.
Figure B2 illustrates the minimum interface to the CS4218. In this application, the DSP sends and
receives stereo DAC and ADC information. The CS4218 is configured for 32 bits per frame, Master
sub-mode. The control data resets to all zeros, which configures the CS4218 as a simple stereo codec:
no gain, no attenuation, line inputs #1, and DAC outputs not muted.
Figure B3 illustrates how to use all the CS4218 features with a low cost DSP that cannot support the
interrupt rate of SM3. Using SM4 (32 bits per frame, Master sub-mode) reduces the DSP interrupts in
half since the control data is split from the audio data. This circuit is comprised of three independent
sections which may individually be eliminated if not needed.
SDOUT ⁴³
SDIN ⁴²
1
SSYNC
SCLK ⁴⁴
DSP
CS4218
SM4
VD+
MF1:CDOUT ⁴⁰
MF2:CDIN ³⁹
MF4:CCS ³⁶
MF3:CCLK ³⁵
MF5:INT ³⁸
RESET ²
MF6:F1 ³⁴
31
MF7:F2
30
MF8:F3
Micro-
Controller
Serial
Port
IRQ
General
Purpose
Port
Pins
Figure B1. SM4 - Microcontroller Interface
40
43
SDOUT
SDIN ⁴²
SSYNC ¹
44
SCLK
CS4218
SM4
32 BPF
35
MF3:CCLK
MF4:CCS ³⁶
MF5:INT ³⁸
40
MF1:CDOUT
MF2:CDIN ³⁹
RESET ²
34
MF6:F1
31
MF7:F2
30
MF8:F3
DSP
VD+
Hard Wired or
DIP Switch
selectable
Figure B2. SM4 - Minimum DSP Interface
DS135F1