Datasheet

OBSOLETE
LM4550
www.ti.com SNAS032F –SEPTEMBER 2001–REVISED APRIL 2013
CODEC CHAINING
Using National Semiconductor's unique feature for chaining together codecs, a multiple codec system can be
built using fewer interface pins. This Chain feature allows two, three or four codecs to share a single signal input
pin at the controller. By setting the two LSBs of the Chain-In Control register (74h) to a value other than the
Codec Identity, a controller can instruct a codec to disconnect its own SDATA_IN signal and discard its own
Input Frame and instead switch the signal connected to the CIN pin through to the SDATA_IN output pin allowing
passage of an SDATA_IN signal carrying the Input Frame from a codec further down the chain. The Chain-In
Control register (74h) is updated at the rising edge of SYNC therefore an instruction to enable or disable the
Chain feature takes effect in the next frame.
When the Chain feature is used the CIN pin should always be driven. Connect CIN to either the SDATA_IN pin
from another codec or else ground CIN to prevent the possibility of floating the SDATA_IN signal at the
controller.
Copyright © 2001–2013, Texas Instruments Incorporated Submit Documentation Feedback 35
Product Folder Links: LM4550