Transcript LCD_Module - Your M2M Solutions Expert

NS9750 - Training
Hardware
NS9750 LCD Block
Overview
• The LCD Controller provides an interface to a STN or TFT
LCD Panel. Display data is DMAed from external memory
to the LCD controller.
To LCD Panel
LCD Controller
AHB BUS
(To Memory)
LCD Controller
• Supports both monochrome and color, single- and dual-panel Super
Twisted Nematic (STN) LCD panels
• Supports 18 and 24-bit Thin Film Transistor (TFT) LCD color displays
• STN mode supports up to 15 gray-levels for monochrome and 3375
colors
• TFT mode supports up to 16M colors
• Supports all popular display resolutions up to 1024x768 maximum
• 256 entry, 16-bit palette RAM
• Monochrome STN supports 1,2, or 4 bits-per-pixel via palette RAM
LCD Controller
• Color STN supports 1,2,4, or 8 bits-per-pixel via palette RAM
• TFT supports 1,2,4,or 8 bits per-pixel via palette RAM; 16 and 24 bits
per pixel direct
• LCD timing programmable
• AHB DMA engine transfers display data from external memory to dual
64x32 FIFOs
• Supports big and little endian pixel format, as well as WinCE
• LCD panel clock can either be generated internally from the AHB
clock or provided via an external oscillator
LCD Controller Programmable Parameters
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Horizontal front porch
Horizontal back porch
Horizontal sync pulse width
Number of pixels per line
Vertical front porch
Vertical back porch
Vertical sync pulse width
Number of lines per panel
Number of panel clocks per line
Signal polarity
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AC panel bias
Panel clock frequency
Number of bits-per-pixel
Display type (STN mono/color
or TFT)
STN 4 or 8 bit interface
STN dual or single panel
Pixel format (little-endian, bigendian or WinCE)
Interrupt generation event
LCD Panel Interface
Signal
Description
CLPOWER
LCD panel power enable
CLLP
Line sync pulse (STN) or horizontal sync pulse (TFT)
CLCP
LCD panel clock
CLFP
Frame pulse (STN) or vertical sync pulse (TFT)
CLAC
AC bias drive (STN) or data enable (TFT)
CLD[23:0]
LCD panel data
CLLE
Line end signal
LCD Setup Procedure
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Setup horizontal timing parameters for LCD panel (e.g. front porch,
back porch, sync width, number of pixels per line)
Setup vertical timing parameters for LCD panel (e.g. front porch,
back porch, sync width, number of lines per panel)
Setup other display parameters (e.g. signal polarity, panel clock
frequency, number of clocks per line)
Enable conditions that cause interrupt from LCD controller (e.g.
vertical compare)
Setup base address in external memory of area to DMA display data
from.
LCD Setup Procedure
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Select clock source (AHB clock, AHB clock divided down, or
external oscillator)
Load initial display data into external memory
Enable control signals to LCD panel by setting LcdEn bit.
System applies contrast voltage VEE
Apply power to LCD panel by setting LcdPwr bit. This drives
CLPOWER active and enables CLD [23:0] to activate display. (see
NS9750 Hardware Reference Manual for detailed description of
power up and power down sequence)
Interrupts will occur during normal operation (e.g. during vertical
sync). The application can use these to update the base address used
for DMA (e.g. double buffered video display).
LCD Panel Clock Generation
• Source of LCD panel clock is programmable via Clock Configuration
Register in SCM
– AHB clock divided by 1,2,4,8
– External clock oscillator (LCDCLK) divided by 2
• LCD controller provides an additional clock divider that can be used to
divide the source clock further to generate the LCD panel clock (see
NS9750 Hardware Reference Manual for programming limitations on
clock divider value)
STN Displays’ Timing Diagrams
CLFP
CLLP
CLD[7:0] Blank
Valid Display Data
Blank Lines
Valid Display Data
Vertical Timing
CLLP
CLCP
CLD[7:0]
Blanking
Valid Display Data
Horizontal Timing
Blanking
TFT Displays’ Timing Diagrams
CLFP
CLLP
Blanking
Active Display Data
Blanking
CLAC
Vertical Timing
CLLP
CLCP
CLAC
CLD[23:0]
Blanking
Active Display Data
Horizontal Timing
Blanking
Hints & Kinks
• Can I directly directly connect the NS9750’s LCD interface signals
to an LCD display panel?
– Although there is nothing functionally wrong with this approach, the
NS9750’s LCD outputs, with the exception of CLCP(8ma), are rated at
only 4ma. Direct connection would only be practical over a few inches of
trace. These drive strengths are definitely not applicable to driving a LCD
panel via a cable. A single, low-skew, high drive buffer is recommended
for applications requiring more drive than the NS9750 can provide. A
single device with low-skew is required because the skew between the
clock and all of the other signals is the key in meeting the timing
requirements of the LCD panel.
Hints & Kinks
• My 24-bit TFT LCD display panel requires differential inputs.
How do I interface the NS9750 to it?
– Most 24-bit TFT panels require LVDS (Low Voltage Differential
Signaling) inputs. These typically require an off-the-shelf LVDS serializer
device to interface the display controller to the display. The NS9750’s
LCD interface can interface directly to the parallel interface of this
serializer. Contact the manufacturer of the LCD display for a
recommendation on which serializer device to use (e.g. National
DS90C385)