sed1355 ETC-unknow, sed1355 Datasheet - Page 187

• Manufacturer Part Number: sed1355
• Description: Sed1355 Embedded Ramdac Lcd/crt Controller
• Manufacturer: ETC-unknow

Epson Research and Development
Vancouver Design Center
6 LCD Power Sequencing and Power Save Modes
6.1 Introduction to LCD Power Sequencing
6.2 Registers
Programming Notes and Examples
Issue Date: 99/04/27
REG[0Dh] Display Mode Register
REG[1Ah] Power Save Configuration Register
Portrait Mode
Power Save
Hardware
Enable
Status
Simultaneous
Option Select
Display
Bit 1
n/a
LCD Power Sequencing allows the LCD power supply to discharge prior to shutting down the LCD
signals. Power sequencing is required to prevent long term damage to the panel and to avoid
unsightly “lines” on power-down and power-up.
The SED1355 performs automatic power sequencing when the LCD is enabled or disabled through
the LCD Enable bit in register [0Dh]. For most applications the internal power sequencing is the
appropriate choice.
There may be situations where the internal time delay is insufficient to discharge the LCD power
supply before the LCD signals are shut down. This section details the sequences to manually power-
up and power-down the LCD interface.
Proper LCD power sequencing dictates that there must be a time delay between the time the LCD
power is disabled and the time the LCD signals are shut down. During power up the LCD signals
must be active prior to applying power to the LCD. This time interval varies depending on the power
supply design. The power supply on the SDU1355 Evaluation board requires 0.5 seconds to fully
discharge. Your power supply design may vary.
LCD Enable normally performs all the required power sequencing. Upon setting LCD Enable to '0'
the system will begin a series of events which include turning off the LCD power supply, waiting
for the power supply to discharge and finally turning off the LCD signals.
LCD Power Disable would be used to manually sequence the events leading to an LCD power-down.
First the program would set LCD Power Disable to '1' to begin discharging the LCD power supply.
After waiting a pre-determined amount of time the software would Disable the LCD signals using
the LCD Enable bit in register [0Dh].
Simultaneous
Option Select
Display
Bit 0
n/a
Bit-Per-Pixel
Select Bit 2
n/a
Bit-Per-Pixel
LCD Power
Select Bit 1
Disable
Bit-Per-Pixel
Select Bit 0
Select Bit 1
Suspend
Refresh
CRT Enable
Select Bit 0
Suspend
Refresh
Mode Enable
X23A-G-003-05
LCD Enable
Software
Suspend
SED1355
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