CS8412 datasheet(12/38 Pages) CIRRUS

12 / 38 page

CS8411 CS8412

DS61F1

high. B0 and B1 select one of three buffer modes

listed in Table 2 and illustrated in Figure 5. In all

modes four bytes of user data are stored. In mode 0,

one entire block of channel status is stored. In mode

1 eight bytes of channel status and sixteen bytes of

auxiliary data are stored. In mode 2, eight bytes of

channel status from each sub-frame are stored. The

buffer modes are discussed in more detail in the

Buffer Memory section. The next bit, CS2/CS1, se-

lects the particular sub-frame of channel status to

buffer in modes 0 and 1, and has no effect in mode

2. When CS2/CS1 is low, sub-frame 1 is buffered,

and when CS2/CS1 is high, sub-frame 2 is buff-

ered. IER/SR selects which set of registers, either

IEnable or status, occupy addresses 0 and 1. When

IER/SR is low, the status registers occupy the first

two addresses, and when IER/SR is high, the IEn-

able registers occupy those addresses. FCEN en-

ables the internal frequency counter. A 6.144 MHz

clock must be connected to the FCK pin as a refer-

ence. The value of the FREQ bits in SR2 are not

valid until two thirds of a block of data is received.

Since FCK and A4, the most significant address bit,

occupy the same pin, A4 is internally set to zero

when FCEN is high. Since A4 is forced to zero, the

upper half of the buffer is not accessible while us-

ing the frequency compare feature. FPLL deter-

mines how FSYNC is derived. When FPLL is low,

FSYNC is derived from the incoming data, and

when FPLL is high, it is derived from the internal

phase-locked loop.

Control Register 2 configures the serial port which

consists of three pins: SCK, SDATA, and FSYNC.

SDATA is always an output, but SCK and FSYNC

can be configured as inputs or outputs. FSYNC and

SDATA can have a variety of relationships to each

other, and the polarity of SCK can be controlled.

The large variety of audio data formats provides an

easy interface to most DSPs and other audio pro-

cessors. SDATA is normally just audio data, but

special modes are provided that output received bi-

phase data, or received NRZ data with zeros substi-

tuted for preamble. Another special mode allows an

asynchronous SCK input to read audio data from

the serial port without slipping samples. In this

mode FSYNC and SDATA are outputs synchro-

nized to the SCK input. Since SCK is asynchronous

to the received clock, the number of SCK cycles

between FSYNC edges will vary.

ROER, when set, causes the last audio sample to be

reread if the error pin, ERF, is active. When out of

lock, the CS8411 will output zeros if ROER is set

and output random data if ROER is not set. The

conditions that activate ERF are those reported in

SR2 and enabled in IER2. Figure 10 illustrates the

modes selectable by SDF2-SDF0 and FSF1-FSF0.

MSTR, which in most applications will be set to

one, determines whether FSYNC and SCK are out-

puts (MSTR = 1) or inputs (MSTR = 0). When

FSYNC and SCK are inputs (slave mode) the audio

Figure 8. Control Register 1

CR1:

FPLL:

0 - FSYNC from RXP/RXN, 1 - FSYNC from PLL

FCEN:

enables freq. comparator (FCK must be 6.144 MHz).

IER/SR:

[X:00,01] 0 - status, 1 - interrupt enable registers.

CS2/CS1: ch. status to buffer; 0 - sub-frame 1, 1 - sub-frame 2.

B1:

with B0, selects the buffer memory mode.

B0:

with B1, selects the buffer memory mode.

RST:

Resets internal counters. Set to “1” for normal operation.

X:02

3210

CR1.

FPLL

FCEN

IER/SR

CS2/CS1

RST

Mode

Buffer Memory Contents

Channel Status

Auxiliary Data

Independent Channel Status

Reserved

Table 2. Buffer Memory Modes

Figure 9. Control Register 2

CR2:

ROER:

Repeat previous value on error (audio data)

SDF2:

with SDF0 & SDF1, select serial data format.

SDF1:

with SDF0 & SDF2, select serial data format.

SDF0:

with SDF1 & SDF2, select serial data format.

FSF1:

with FSF0, select FSYNC format.

FSF0:

with FSF1, select FSYNC format.

MSTR:

When set, SCK and FSYNC are output

SCED:

When set, falling edge of SCK outputs data.

When clear, rising edge of SCK outputs data.

X:03

76543210

CR2.

ROER

SDF2

SDF1

SDF0

FSF1

FSF0

MSTR

SCED

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