CS5535 datasheet(90/555 Pages) NSC

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ACC Functional Description (Continued)

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Audio Driver Power-up/down Programming Model

The ACC contains Machine Specific Registers (MSRs) that

relate to a very low level power management scheme, but

are discrete from the power management features of the

codec and the device driver programming model. This sec-

tion covers the power management features for the device

driver.

See Section 4.3.5 "AC Link Power Management" on page

86 for power management hardware details.

The following sections outline how the device driver should

perform power management.

Power-down Procedure

Disable or pause all bus masters using their bus mas-

ter command register.

It may be necessary to determine if a second codec is

being used, and if so, verify that the power-down

Semaphore for Secondary Codec bit is set before pro-

ceeding (to insure that the modem driver has prepared

the second codec for power-down, if necessary).

Using the Codec Control register, access the primary

codec’s registers and program the codec to power-

down. Also, simultaneously write to the AC Link Shut-

down bit in the Codec Control register (ACC I/O Offset

0Ch[18]).

The ACC and codec will power-down once the com-

mand is received by the codec. All of the contents of

the ACC and codec registers are preserved during the

power-down state.

If you wish to enable the GPIO wakeup interrupt, wait

for an additional two audio frame periods (42 µs)

before setting the GPIO Wakeup Interrupt Enable bit

(ACC I/O Offset 00h[29]). Failure to wait will cause

false interrupt events to occur.

Power-up Procedure

If GPIO Wakeup Interrupt Enable (ACC I/O Offset

00h[29]) was set in the power-down procedure, it will

automatically be disabled upon power-up.

Set the AC Link Warm Reset bit in the Codec Control

warm reset sequence.

Wait for the Codec Ready bit(s) in the Codec Status

before accessing any codec features or enabling any

bus masters.

Notes:

If the GPIO Wakeup Interrupt Enable (ACC I/O Offset

00h[29]) is set, and an interrupt occurs, it is detected

and fired, but the interrupt does not wakeup the codec

and ACC. The hardware will only wakeup if the soft-

ware responds to the interrupt and performs the

power-up procedure.

Once software has issued a power-down, it must not

perform the power-up procedure for at least six audio

frame periods (about 0.125 ms or 125 µs). Doing so

could lock up the codec or ACC.

If the system has cut off power to the codec and

restarted it, it is not necessary to initiate a warm reset.

The AC Link Shutdown should be cleared manually to

restart the operation of the AC Link.

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