SPC8104 S-MOS Systems, SPC8104 Datasheet - Page 186

• Manufacturer Part Number: SPC8104
• Description: VGA LCD CONTROLLER
• Manufacturer: S-MOS Systems

3.0
To set a powerdown mode, one has to assume the worst case scenario, i.e. we already are in a
powerdown mode, the oscillator is disabled and only ports 3DEh/3DFh are decoded. Every pow-
erdown sequence therefore first powers the chip up to a known state and then powers the chip
down to the requested state. Note that a small delay is needed after the oscillator is re-enabled,
this is to accommodate for the fact it takes a finite amount of time for the oscillators to start oscil-
lating after being enabled.To avoid any visual anomalies or to ensure proper powerdown timings,
most powerdown sequences wait for several frames, this is accomplished by counting vertical
retraces. (To do this, we must have full address decoding enabled.)
Powerdown sequences are summarized in the following tables.
The powerdown Mode 4 comes in two flavors, if we have any PD clock, we can disable the oscil-
lator. If the PD clock is CLOCKI, we cannot disable the oscillator, as we would in essence disable
the PD clock itself. The presence of the PD clock is determined at run-time based on the MD
lines.
All power down modes are programmed using AUX[03h]. There are three power down modes
available:
For doze mode 2 we can optionally program automatic clock division, suspend mode can disable
CLKI altogether, providing we have specified different DRAM refresh clock in AUX[02h].
The following is pseudo-code to illustrate how to set individual power save modes regardless of
the current power save mode. The lines marked with * are needed if we want to shut down CLKI in
suspend mode:
Programming Notes and Examples
SP3-32
Doze Mode 1:
*
*
Doze Mode 2:
*
*
Suspend:
*
*
*
*
*
*
Full Power:
*
MANUAL SETTING OF POWER STATES ON THE SPC8104
S-MOS Systems, Inc. • Tel: [phone] • Fax: [phone] • http://www.smos.com
AUX[03h] &= 11101111b ; Make sure CLKI Enabled
AUX[03h] &= 00001101b ; clear all power down modes (Full Power)
AUX[03h] |= 10100000b ; set doze mode 1
AUX[03h] &= 11101111b ; Make sure CLKI Enabled
AUX[03h] &= 00001101b ; clear all power down modes (Full Power)
AUX[03h] |= 11000000b ; set doze mode 2
AUX[03h] &= 11101111b ; Make sure CLKI Enabled
AUX[03h] &= 00001101b ; clear all power down modes (Full Power)
AUX[03h] |= 00000010b ; keep CLKI, suspend
Wait For Vsync
Wait For Vsync
Wait For Vsync
AUX[03h] |= 00010000b ; kill CLKI
AUX[03h] &= 11101111b ; Make sure CLOCKI Enabled
AUX[03h] &= 00001101b ; clear all power down modes (Full Power)
•
•
•
doze mode 1
doze mode 2
suspend
; wait for at least 3 vertical frames
; before shutting down CLKI
412-1.0
SPC8104