CMI9738 Datasheet, PDF (16/36 Pages) List of Unclassifed Manufacturers – Integrated Multi-channel AC97

CMI 9738
Integrated Multi-channel AC‘97
Audio output frame slot 12 is reserved for modem operations and is not used by the CMI9738.
4.7 AC-LINK LOW POWER MODE
The CMI9738 AC-Link can be placed in the low power mode by programming register 26h to the
appropriate value. Both BIT_CLK and SDATA_IN will be brought to, and held at a logic low
voltage level. The AC'97 controller can wake up the CMI9738 by providing the appropriate reset
signals.
Figure 7. AC-link Powerdown Timing
BIT_CLK and SDATA_IN are transitioned low immediately (within the maximum specified time)
following the decode of the write to the Powerdown Register (26h) with PR4. When the AC'97
controller driver is at the point where it is ready to program the AC-Link into its low power mode,
slots (1 and 2) are assumed to be the only valid stream in the audio output frame (all sources of
audio input have been neutralized).
The AC'97 controller should also drive SYNC and SDATA_OUT low after programming the
CMI9738 to this low power mode.
Waking up the AC-link
Once the CMI9738 has halted BIT_CLK, there are only two ways to “wake up” the AC-Link.
Both methods must be activated by the AC'97 controller. The AC-Link protocol provides for a
“Cold AC'97 Reset”, and a “Warm AC'97 Reset”. The current power down state would ultimately
dictate which form of reset is appropriate. Unless a “cold” or “register” reset (a write to the Reset
register) is performed, wherein the AC'97 registers are initialized to their default values, registers
are required to keep state during all power down modes. Once powered down, re-activation of the
AC-Link via re- assertion of the SYNC signal must not occur for a minimum of 4 audio frame
times following the frame in which the power down was triggered. When AC-Link powers up it
indicates readiness via the Codec Ready bit (input slot 0, bit 15).
C-MEDIA Electronics Inc.
6F, 100, Sec. 4, Civil Boulevard, Taipei, Taiwan, R.O.C. 106
TEL: [phone] FAX: [phone] E-mail:[e-mail]
Revision Date Apr./2002
Revision 1.1