Samsung YP-P10 User Manual Page 544

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S3C2440A RISC MICROPROCESSOR AC97 CONTROLLER
24-7
AC97 POWERDOWN
SDATA_OUT
SDATA_IN
BIT_CLK
SYNC
slot 12
prev.frame
Write to
0X26
slot 12
prev.frame
TAG
TAG
Data
PR4
Figure 24-7. AC97 Powerdown Timing Diagram
Powering Down the AC-link
The AC-link signals enter a low power mode when the AC97 CODEC Powerdown register (0x26) bit PR4 is set to 1
(i.e. by writing 0x1000). Then the Primary CODEC drives both the BITCLK and SDATA_IN to a logic low voltage level.
The sequence follows the timing diagram shown above in the Figure 24-7.
The AC97 Controller transmits the write to Powerdown 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 Powerdown 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 the SYNC and SDATA_OUT to a logic low level after programming the AC_GLBCTRL register.
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