CP3SP33SMSSLASHNOPB datasheet(243/407 Pages) TI1

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CP3SP33

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SNOSCW5 – MAY 2013

TMD

The Transmit Master DMA field specifies which slots (audio channels) are supported by DMA,

i.e., when a DMA request is asserted to the DMA controller. If the TMD field is set for an

assigned slot (TXDSAn = 1), a DMA request is asserted when the ATDRn register is empty. If

the TXDSA bit for a slot is clear, the TMD field is ignored. The following table shows the transmit

DMA request scheme.

TMD FIELD

DMA REQUEST CONDITION

0000

None

0001

ATDR0 empty

0010

ATDR1 empty

0011

ATDR0 empty or ATDR1 empty

x1xx

Not supported on CP3SP33

1xxx

ACD

The Audio Control Data field is used to fill the remaining bits of a 16-bit slot if only 13, 14, or 15

bits of PCM audio data are transmitted.

ACO

The Audio Control Output field controls the number of control bits appended to the PCM data

word.

00 – No Audio Control bits are appended.

01 – Append ACD0.

10 – Append ACD1:0.

11 – Append ACD2:0.

24.8 Usage Example

The following example shows the AAI being used to interface to two single-channel codecs. The interface

has the following characteristics:

•

Synchronous mode

•

8-bit data word

•

Network mode with 4 slots per frame

•

Slot 0 is assigned for Audio interface - Codec 1 communication (receive and transmit)

•

Slot 1 assigned for Audio interface - Codec 2 communication (receive and transmit)

•

Slots 2 and 3 unused

•

Internal long frame synch pulse

•

Internal shift clock, adjusted to achieve a 64 kb/s log PCM audio quality

•

Frame rate set to 8 kHz (see below)

•

Bit clock set to 256 kHz (see below)

It is not currently possible for the AAI to produce an exact 8 kHz frame rate together with an exact 256

kHz bit rate from a 12-MHz clock input. If this is used in a system containing a component that requires

data at a frame rate of precisely 8 kHz (including the CVSD/PCM converter), then an audio artifact may be

produced. If a PLL clock generator is available, it can be used to provide an input clock of the frequency

required to provide suitable derivative frequencies.

Figure 24-11 shows the connections between the AAI and the external codecs. Figure 24-12 shows the

timing of the interface.

Advanced Audio Interface

243

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