SPC8104 S-MOS Systems, SPC8104 Datasheet - Page 74

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

10.0 POWER SAVE MODES
10.1 Power Save Modes
To accommodate the important need for power reduction in sub-notebook and palmtop comput-
ers, three Power Save Modes, Doze mode 1, Doze mode 2, and Suspend, have been incorpo-
rated into the SPC8104. All Power save modes are software-controlled or hardware-controlled.
Additional options for these Power Save Modes can be enabled by setting bits in various Auxiliary
registers, allowing flexibility in tailoring the power reduction scheme to any particular system
implementation.
Suspend mode can be activated through input pin SUSPEND# or by enabling the Suspend Mode
Enable bit in the Power Save Register (AUX[03]). There are some small differences between
hardware Suspend mode and software Suspend mode. Hardware Suspend mode will override
software Suspend mode. Doze mode can be activated through input pin DOZE# or by enabling
the Doze Mode Enable bit. The Doze mode select bits determine the function of the Doze mode.
Hardware Doze mode and software Doze mode are functionally identical. Whether hardware acti-
vated or software activated, Suspend mode always overrides Doze mode. The following descrip-
tions outline the major functions of each power save mode. See the following tables and notes for
more information.
Doze Mode 1
Doze Mode 1 is intended to be used with RAM type LCD driver in order take advantage of its self-
refresh mode. This power save mode has an Active State and a Power Down State. Initially the
chip enters the Active state which is functionally the same as the normal operation. If there is no
memory or I/O write for at least two vertical frames, the output pixels are first re-mapped to black
and white. After two more frames with no memory or I/O write, XSCL is stopped to put the LCD
driver into its self-refresh mode. In such a self-refresh mode, the binary image stored in the inter-
nal RAM of the LCD driver is used to refresh the LCD panel. Various internal blocks in the
SPC8104 are also shut down. The chip is now in the Power Down State. Upon detecting a mem-
ory or I/O write, the disabled internal blocks are re-enabled and XSCL is reactivated at the begin-
ning of the next frame or the second to next frame. With XSCL reactivated, the LCD driver leaves
its self-refresh mode. The chip returns to the Active State and the above sequence repeats.
Hardware Functional Specification
SP1-48
Mode Enable
Suspend
S-MOS Systems, Inc. • Tel: [phone] • Fax: [phone] • http://www.smos.com
0
0
0
0
1
Doze Mode
Power Save Register Bits
Enable
X
0
1
1
1
Table 0-33 Power Save Mode Selection
Doze Mode 2
Select
X
X
0
1
1
X15-SP-001-08.1
Doze Mode 1
Select
X
X
1
0
1
Normal Operation
Doze Mode 1
Doze Mode 2
Doze Mode 1 and 2
Software Suspend Mode
Mode Activated
412-1.0
SPC8104