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Preliminary
S3C2451 RISC MICROPROCESSOR AC97 CONTROLLER
27-9
Preliminary product information describe products that are in development,
for which full characterization data and associated errata are not yet available.
Specifications and information herein are subject to change without notice.
AC97 POWER-DOWN
For details, please refer the AC-Link Power Managerment part of AC97 revision 2.0 specification.
SDATA_OUT
SDATA_IN
BIT_CLK
SYNC
slot 12
prev.frame
Write to
0X26
slot 12
prev.frame
TAG
TAG
Data
PR4
Figure 27-7. AC97 Power-down Timing
Powering Down the AC-link
The AC-link signals enter a low power mode when the AC97 Codec Power-down register (0x26) bit PR4 is set
to a 1 (by writing 0x1000). Then the Primary Codec drives both BITCLK and SDATA_IN to a logic low voltage
level. The sequence follows the timing diagram shown in Figure 27-7.
The AC97 Controller transmits the write to Power-down register (0x26) over the AC-link. Set up the AC97
Controller so that it does not transmit data to slots 3-12 when it writes to the Power-down register bit PR4 (data
0x1000), and it does not require the Codec to process other data when it receives a power down request. When
the Codec processes the request it immediately transitions BITCLK and SDATA_IN to a logic low level. The AC97
Controller drives SYNC and SDATA_OUT to a logic low level after programming the AC_GLBCTRL register.
Waking up the AC-link - Wake Up Triggered by the AC97 Controller
AC-link protocol provides 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 times 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).