wm9704m Wolfson Microelectronics plc, wm9704m Datasheet - Page 28

• Manufacturer Part Number: wm9704m
• Description: Amc97 Audio Modem Codec
• Manufacturer: Wolfson Microelectronics plc

WM9704M
WOLFSON MICROELECTRONICS LTD
Figure 13 An Example of the WM9704M Powerdown/Powerup Flow
Figure 13 illustrates one example procedure to do a complete powerdown of the WM9704M. From
normal operation sequential writes to the Powerdown Register are performed to powerdown the
WM9704M a piece at a time. After everything has been shut off (PR0 to PR3 set), a final write (of
PR4) can be executed to shut down the WM9704M’s digital interface (AC-link).
The part will remain in sleep mode with all its registers holding their static values. To wake up the
WM9704M, the AC’97 controller will send a pulse on the sync line issuing a warm reset. This will
restart the WM9704M’s digital interface (resetting PR4 to 0). The WM9704M can also be woken up
with a cold reset. A cold reset will cause a loss of values of the registers, as a cold reset will set them
to their default states. When a section is powered back on, the Powerdown Control/Status register
(index 26h) should be read to verify that the section is ready (i.e. stable) before attempting any
operation that requires it.
Alternatively if RESETB is held low, all PR bits are held set so the device is held powered off until
RESETB is taken high again.
Figure 14 The WM9704M Powerdown/Flow with Analogue Still Alive
Figure 14 illustrates a state when all the mixers should work with the static volume settings that are
contained in their associated registers. This is used when the user could be playing a CD (or external
LINE_IN source) through WM9704M to the speakers but have most of the system in low power
mode. The procedure for this follows the previous except that the analogue mixer is never shut down.
NORMAL
ADCs OFF
PR0 = 0 AND
PR0
ADC = 1
PR0 = 1
DAC = 1
PR1 = 0
PR1 = 1
AND
READY = 1
ADCs OFF
PR0
PR1 = 0 AND
DACs OFF
DAC = 1
PR1
PR1 = 1
PR2 = 0 AND
DACs OFF
PR2 = 1
ANL = 1
PR1
PR2 = 0 AND
OFF PR2 OR
ANALOGUE
ANL = 1
DEFAULT
PR2 = 1
PR3
OFF PR2 OR
ANALOGUE
PR4 = 1
PR3
WARM RESET
PR4 = 1
DIGITAL I/F
OFF PR4
COLD RESET
DIGITAL I/F
OFF PR4
WARM
RESET
PD Rev 3.2 January 2001
CODA LINK
SHUT OFF
Production Data
CODA LINK
SHUT OFF
28