DR
Internal FSR
W1
W3
RRDY
RB to DRR
copy (W3)
Read of
DRR (W3)
Read of
DRR (W3)
RB to DRR
copy (W1)
RB to DRR
copy (W3)
DX
Internal FSX
W3
XRDY
DXR to XSR
copy (W1)
Write of DXR
(W3)
DXR to XSR
copy (W3)
mcbsp-047
Public Version
McBSP Functional Description
www.ti.com
Figure 21-52. Activity on McBSP Pins When XMCM=0b11
In
if XMCM = 0b11, RPABLK = 0b00, XPABLK = 0bX, RCERA = 0b1010 and XCERA =
0b1000, channels 1 and 3 are enabled in receive and transmit mode, but only 3 unmasked. Words W1
and W3 are written to the XB, but only W3, from the XB, there are transferred by mcbspi_dx.
21.4.7 SIDETONE Mode (ALP)
21.4.7.1 Introduction
In multimedia-rich mobile communication devices, loopback signals from audio inputs to audio outputs are
renamed. A traditional example is the telephone SIDETONE (that is, the telephone user expects to also
hear his own voice in the earpiece).
Some of the features using the loopback have strict delay requirements.
It is required that two of the audio input channels be looped back, filtered, and mixed to the corresponding
two audio output channels. The SIDETONE mode filters and applies gain to each sample received.
21.4.7.2 SIDETONE Interface
The data from digital microphone, two (out of four) channels, can be configured to be input in the external
SIDETONE core. After filtering, the data from digital microphone data is mixed and sent out to the speaker
output channels using two (out of eight) configured output channels (separate configuration bits are used).
The McBSP module synchronizes the incoming data (filtered by the external SIDETONE core). The
transmit and receive part of the McBSP module are not required to operate on the same functional
frequency.
The SIDETONE interface offers the following features:
•
Send out two 24-bit data channels for the configured SIDETONE received channels (channels can be
the same)
•
Send out two control signals to indicate to the SIDETONE module that the data is valid (toggle signals
which are changing the value from 0 to 1 or 1 to 0 each time a new data is available)
•
Receive two 24-bit filtered data channels from the external SIDETONE module and send these
channels to the configured transmit channels after mixing the data with the incoming data (from the L4
interface). The sum between the incoming data and SIDETONE loopback data is a saturated sum.
•
Receive two control signals to indicate that the SIDETONE module filtered data is available (toggle
signals which are changing the value from 0 to 1 or 1 to 0 each time a new data is available).
3120
Multi-Channel Buffered Serial Port
SWPU177N – December 2009 – Revised November 2010
Copyright © 2009–2010, Texas Instruments Incorporated
