EP7212 datasheet(39/136 Pages) CIRRUS

39 / 136 page

EP7212

DS474PP1

3.13.1

Codec Sound Interface

The codec interface allows direct connection of a

telephony type codec to the EP7212. It provides all

the necessary clocks and timing pulses. It also per-

forms a parallel to serial conversion or vice versa

on the data stream to or from the external codec de-

vice. The interface is full duplex and contains two

separate data FIFOs (16 deep by 8-bits wide, one

for the receive data, another for the transmit data).

Data is transferred to or from the codec at

64 kbits/s. The data is either written to or read from

the appropriate 16-byte FIFO. If enabled, a codec

interrupt (CSINT) will be generated after every

8 bytes are transferred (FIFO half full/empty). This

means the interrupt rate will be every 1 msec, with

a latency of 1 msec.

Transmit and receive modes are enabled by assert-

ing high both the CDENRX and CDENTX codec

enable bits in the SYSCON1 register.

NOTE:

Both the CDENRX and CDENTX enable bits

should be asserted in tandem for data to be

transmitted or received. The reason for this

is that the interrupt generation will occur

1 msec after one of the FIFOs is enabled.

For example: If the receive FIFO gets

enabled first and the transmit FIFO at a later

time, the interrupt will occur 1 msec after the

receive FIFO is enabled. After the first inter-

rupt occurs, the receive FIFO will be half full.

However, it will not be possible to know how

full the transmit FIFO will be since it was

enabled at a later time. Thus, it is possible to

unintentionally overwrite data already in the

transmit FIFO (See Figure 6).

After the CDENRX and CDENTX enable bits get

asserted, the corresponding FIFOs become en-

abled. When both FIFOs are disabled, the FIFO sta-

Type

Comments

Referred To As

Max. Transfer Speed

SPI / Microwire 1

Master mode only

ADC Interface

128 kbits/s

SPI / Microwire 2

Master / slave mode

SSI2 Interface

512 kbits/s

DAI Interface

CD quality DACs and ADCs

DAI Interface

1.536 Mbits/s

Codec Interface

Only for use in the PLL clock mode

Codec Interface

64 kbits/s

Table 21. Serial Interface Options

No.

LQFP

External

Pin Name

SSI2

Slave Mode

(Internal Name)

SSI2

Master Mode

Codec

Internal Name

DAI

Internal Name

Strength

SSICLK

SSICLK = serial bit

clock; Input

Output

PCMCLK =

Output

SCLK =

Output

SSITXFR

SSKTXFR = TX

frame sync; Input

Output

PCMSYNC = Output

LRCK = Output

SSITXDA

SSITXDA = TX

data; Output

Output

PCMOUT = Output

SDOUT = Output

SSIRXDA

SSIRXDA = RX

data; Input

Input

PCMIN = Input

SDIN = Input

SSIRXFR

SSIRXFR = RX

frame sync; Input

Output

p/u

(use a 10k pull-up)

MCLK

Table 22. Serial-Pin Assignments

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