CS1311 datasheet(19/25 Pages) NSC

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Signal Definitions (Continued)

2.2.7

Audio Out Interface Signals

Signal Name

Ball

No.

Type

Description

AO_OSCLK

B14

Over-Sampling Clock. This output can be programmed to emit any fre-

quency up to 40 MHz, with a sub-Hertz resolution. It is intended for use

as the 256 or 384 fs over-sampling clock by the external D/A conversion

subsystem. A board-level 27 to 33

Ω series resistor is recommended to

reduce ringing.

AO_SCK

A14

I/O

Serial Clock. When the Audio Out (AO) module is programmed to act as

the serial interface timing slave (power-up default), AO_SCK acts as an

input. It receives the Serial Clock from the external audio D/A sub-

system. The clock is treated as fully asynchronous to the

CS1301/CS1311 main clock.

When the AO module is programmed to act as the serial interface timing

master, AO_SCK acts as an output. It drives the serial clock for the

external audio D/A subsystem. The clock frequency is a programmable

integral divisor of the AO_OSCLK frequency. AO_SCK is limited to 22

MHz. The sample rate of valid samples embedded within the serial

stream is variable. If used as an output, a board-level 27 to 33

Ω series

resistor is recommended to reduce ringing.

AO_SD1

B13

Serial Data Buses. Serial data to external stereo audio D/A subsystem.

The timing of transitions on this output is determined by the

CLOCK_EDGE bit in the AO_SERIAL register, and can be on positive or

negative AO_SCK edges.

AO_SD2

A13

AO_SD3

C12

AO_SD4

B12

AO_WS

A15

I/O

Word-Select or Frame synchronization. Signal from/to the external

D/A subsystem. Each audio channel receives 1 sample for every WS

period.

When the AO module is programmed as the serial interface timing slave

(power-up default), AO_WS acts as an input. AO_WS is sampled on the

opposite AO_SCK edge from which AO_SDx are asserted.

When the AO module is programmed as serial interface timing master,

AO_WS acts as an output. AO_WS is asserted on the same AO_SCK

edge as AO_SDx.

Note:

The AO module always acts as sender, but can be master or slave for D/A timing.

2.2.8

S/PDIF Interface Signals

Signal Name

Ball

No.

Type

Description

SPDO

A12

S/PDIF Data Out. Self-clocking serial data stream as per IEC958, with

1937 extensions. Note that the low impedance output buffer requires a

27 to 33

Ω series terminator close to CS1301/CS1311 in order to match

the board trace impedance. This series terminator must be part of the

voltage divider needed to create the coaxial output through the AC isola-

tion transformer.

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