Power Management - Compaq Armada e500 Series Reference Manual

Power Management

The ES1921 is capable of operating at reduced power when no activity is required. The
state of power-down is controlled by the power-down control/status register (26h).
There are seven separate power states: PR0 through PR6.
Figure 6-5 illustrates an example procedure for powering down the ES1921. From
normal operation, sequential writes to the power-down control/status register 26h are
performed to power down the ES1921 subsection by subsection. After everything has
been powered down, a final write (of PR4) shuts down the AC-Link. The ES1921
remains in sleep mode with all its registers holding their static values.
PR0=1
Normal
PR0=0
ADC=1
Figure 6-5. Example of Power-Down/Power-Up Flow
A warm reset or a cold reset returns the ES1921 to a wakened state. To wake up the
ES1921, the Maestro Digital Controller sends a pulse on the SYNC line issuing a warm
reset. This restarts the AC-Link (resetting PR4 to zero). A cold reset also wakes up the
ES1921. However, a cold reset causes a loss of context, as a cold reset returns the
ES1921 registers to their default states. When a subsection is powered back on, the
power-down control/status register 26h should be read to verify that the subsection is
ready (stable) before attempting any operation that requires that subsection.
6-14 Audio Subsystem
PR1=1
PR0 PR1
ADCs off DACs off
PR1=0
DAC=1
Ready=1
Digital I/F off
PR5=1
PR2=1 PR4=1
PR2 or PR3
Analog off Digital I/F off
PR2=0
ADC=1
Default
AC-Link off Oscillator Off
PR4 Shut off
AC-Link
Warm Reset
Cold Reset