Samsung YP-P10 User Manual Page 545

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AC97 CONTROLLER S3C2440A RISC MICROPROCESSOR
24-8
Waking up the AC-link - Wake Up Triggered by the AC97 Controller
AC-link protocol is provided for a cold AC97 reset and a warm AC97 reset. The current power-down state ultimately
dictates which AC97 reset is used. Registers must stay in the same state during all power-down modes unless a
cold AC97 reset is performed. In a cold AC97 reset, the AC97 registers are initialized to their default values. After a
power down, the AC-link must wait for a minimum of four audio frame time after the frame in which the power down
occurred before it can be reactivated by reasserting the SYNC signal. When AC-link powers up, it indicates
readiness through the Codec ready bit (input slot 0, bit 15).
Analog
off PR2
or PR3
Digital
I/F off
PR4
Shut off
AC-link
DACs off
PR1
ADCs off
PR0
Normal
DefaultReady = 1
PR0 = 0
&
ADC = 1
PR1 = 0
&
ADC = 1
PR2 = 0
&
ANL = 1
Warm Reset
Cold Reset
PR0 = 1 PR1 = 1 PR2 = 1 PR4 = 1
Figure 24-8. AC97 Power down/Power up Flow
Cold AC97 Reset
A cold reset is generated when an nRESET pin is asserted through the AC_GLBCTRL. Asserting and de-asserting
nRESET activates the BITCLK and SDATA_OUT. All the AC97 control registers are initialized to their default power
on reset values. nRESET is an asynchronous AC97 input.
Warm AC97 Reset
A warm AC97 reset reactivates the AC-link without altering the current AC97 register values. A warm reset is
generated when BITCLK is absent and SYNC is driven high. In normal audio frames, SYNC is a synchronous AC97
input. When BITCLK is absent, SYNC is treated as an asynchronous input used to generate a warm reset to
AC97.The AC97 Controller must not activate BITCLK until it samples the SYNC to low again. This prevents a new
audio frame from being falsely detected.
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