CS4299 datasheet(33/52 Pages) CIRRUS

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CS4299

5. POWER MANAGEMENT

5.1

AC ’97 Reset Modes

The CS4299 supports three reset methods, as de-

fined in the AC ’97 Specification: Cold AC ’97 Re-

set, Warm AC ’97 Reset, Register AC ’97 Reset. A

Cold Reset results in all AC ’97 logic (registers in-

cluded) initialized to its default state. A Warm Re-

set leaves the contents of the AC ’97 register set

unaltered. A Register Reset initializes only the

AC ’97 registers to their default states.

5.1.1

Cold AC ‘97 Reset

A Cold Reset is achieved by asserting RESET# for

a minimum of 1 µs after the power supply rails

have stabilized. This is done in accordance with the

minimum timing specifications in the AC ’97 Seri-

al Port Timing section on page 7. Once deasserted,

all of the CS4299 registers will be reset to their de-

fault power-on states and the BIT_CLK and

SDATA_IN signals will be reactivated.

5.1.2

Warm AC ’97 Reset

A Warm Reset allows the AC-link to be reactivated

without losing information in the CS4299 registers.

A Warm Reset is required to resume from a D3hot

state, where the AC-link had been halted yet full

power had been maintained. A primary codec

Warm Reset is initiated when the SYNC signal is

driven high for at least 1 µs and then driven low in

the absence of the BIT_CLK clock signal. The

BIT_CLK clock will not restart until at least 2 nor-

mal BIT_CLK clock periods (162.8 ns) after the

SYNC signal is deasserted. A Warm Reset of the

secondary codec is recognized when the primary

codec on the AC-link resumes BIT_CLK genera-

tion. The CS4299 will wait for BIT_CLK to be sta-

ble to restore SDATA_IN activity and/or S/PDIF

transmission on the following frame.

5.1.3

The third reset mode provides a Register Reset to

the CS4299. This is available only when the

CS4299 AC-link is active and the Codec Ready bit

is ‘set’. The audio (including extended audio) reg-

isters (Index 00h - 38h) and the vendor specific reg-

isters (Index 5Ah - 7Ah) are reset to their default

states by a write of any value to the Reset Register

(Index 00h).

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