Avnet Display Spec 1 00(1)

7/31/2019 Avnet Display Spec 1 00(1)

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Avnet LCD Interface Specification(ALI)

Revision 1.00


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avnet-display-spec-1 00 (2).doc Avnet Inc

Contents

1 Revision History............................................................................................................................................................42 Defini tions .....................................................................................................................................................................43 Disclaimer......................................................................................................................................................................44 Introduction ...................................................................................................................................................................5

4.1 Scope of this Document ......................................................................................................................................... 54.2 Interface to 3rd party Development Boards.............................................................................................................64.3 Direct Mating of Hosts and Displays.......................................................................................................................64.4 Types of Displays...................................................................................................................................................64.5 Supported Display Interfaces ................................................................................................................................. 6

4.5.1 Parallel ALI ........................................................................................................................................................ 74.5.2 Serial ALI ........................................................................................................................................................... 7

4.6 Supported Backlight Interfaces...............................................................................................................................74.7 Touchscreen Interfaces..........................................................................................................................................74.8 Serial Communications Interfaces..........................................................................................................................74.9 Power.....................................................................................................................................................................7

5 Electr ical Specif ication.................................................................................................................................................85.1 Parallel ALI and Serial ALI ..................................................................................................................................... 85.2 Interface Signal Table ............................................................................................................................................ 95.3 Interface Pinout .................................................................................................................................................... 105.4 Connector Interfaces............................................................................................................................................ 11

5.4.1 Display Interface: Parallel ................................................................................................................................ 115.4.2 Display Interface: Serial ................................................................................................................................... 135.4.3 I2C ................................................................................................................................................................... 135.4.4 SPI................................................................................................................................................................... 145.4.5 Display Control Signals.................................................................................................................................... 145.4.6 Touchscreen Signals ....................................................................................................................................... 15

5.5 Power................................................................................................................................................................... 165.5.1 3.3V Power (PWR33V) .................................................................................................................................... 175.5.2 5V Power (PWR5V) ......................................................................................................................................... 175.5.3 Use of an External Power Supply .................................................................................................................... 17

5.6 Parallel ALI Example............................................................................................................................................ 175.7 Serial ALI Example............................................................................................................................................... 18

6 Physical Specification ................................................................................................................................................186.1 Connector............................................................................................................................................................. 18

6.1.1 Host / Display Direct Connection (Stacked Configuration)...............................................................................196.1.2 Connector Pin-out Mirroring (Stacked Connection)..........................................................................................196.1.3 Silkscreen Identification of Parallel and Serial ALI...........................................................................................20

6.2 Cable.................................................................................................................................................................... 20

Version: 1.00 2 of 20 Revised: 3/9/2010 4:26 PM


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Tables

Table 1 - Interface Signal List .................................................................................................................................................. 9Table 2 LVCMOS33 Signal Specifications for Parallel Video Bus (Parallel ALI Only)......................................................... 11Table 3 - Example: Mapping an 18-bit host into an 18-bit display through the connector..................................................... 12Table 4 Parallel ALI Color Bus Showing Various Modes .................................................................................................... 12Table 5 LVDS Signal Specifications (Serial ALI Only) ........................................................................................................ 13Table 6 - I2C Bus Termination............................................................................................................................................... 14

Table 7 - SPI Bus Termination............................................................................................................................................... 14Table 8 PWM_DIM, ON_OFF, RESET_N, IRQ_N Signal Termination...............................................................................15Table 10 - TOUCH_x (Resistive Touchscreen) Termination..................................................................................................16Table 11 - ALI Connector Compatible Part Numbers............................................................................................................. 18

Figures

Figure 1 Typical Avnet Development Board / Display Kit Configuration................................................................................5Figure 2 - Interface to 3rd Party Development Boards, Showing Interposer.............................................................................6Figure 3 Serial and Parallel ALI Connector I/O (Host Side) .................................................................................................. 8Figure 4 - Parallel and Serial ALI Host Connector Pin-out, Top View....................................................................................10

Figure 5 Using a 74LCX244 to Drive the Line..................................................................................................................... 11Figure 6 - LVDS Point-to-Point Termination........................................................................................................................... 13Figure 7 - Example of I2C Voltage Translation (Display Adapter Side) ................................................................................. 14Figure 8 - Two Methods to Prevent Simultaneous Connection of Touchscreen Signals........................................................ 16Figure 9 Termination of Unused TOUCH_x Signals on the Host Board and Display Board ............................................... 16Figure 10 Parallel ALI Host and Display Adapter Example (with SPI-based TSC) ............................................................. 17Figure 11 Serial ALI Host and Display Adapter Example (with I2C-based TSC) ................................................................ 18Figure 12 - Picture of Tyco AMP-LATCH Type Header and 3M Receptacle.......................................................................... 18Figure 13 Direct Stacking of Display and Host Board ......................................................................................................... 19Figure 14 Parallel ALI Pin-out for Host and Display (Top and Bottom views) ..................................................................... 19Figure 15 Cabled Connection of Display and Host Board................................................................................................... 20



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1 Revision HistoryRevision Date Comments and Major Changes/Updates0.1 2 Sept 2008 Document started

0.2 3 Sept 2008 Added termination information, more definitions, section on interfacing to 3rd party boards,and cable information.

0.3 9 Sept 2008 Grammatical changes.0.4 11 Sept 2008 Multiple changes.

0.5 11 Sept 1008 Changed Serial ALI to 50-pin connector. Candidate for sign-off

0.6 12 Sept 2008 Minor changes based on feedback. Candidate for sign-off

0.7 15 Sept 2008 Eliminated separate connector for Serial ALI. Candidate for sign-off.

0.8 16 Sept 2008 Changed name of VCLK to CLK to avoid confusion in customer base. Added logos.Changed paragraph justification. Candidate for sign-off.

0.9 19 Sept 2008 Added requirements for silkscreen marking of parallel and serial ALI connectors.

0.91 25 Sept 2008 Added IRQ_N signal to specification.

0.92 16 Jan 2009 Specified ON_OFF signal as controlling the display backlight only.Specified an alternate Molex P/N for ALI Host Connector

Added allowance to use shrouded male headers for both host and display. Removed thedrawing of a cabled stacked display configuration.

1.00 8 Mar 2010 Added disclaimer. Public as-is release.

2 DefinitionsThe following terms are used in the context of this specification:

Host: The board containing the processor, FPGA, or other such device generating video signals of the display. This boardgenerates the video signals that are sent to the display. Typically this will be an evaluation board designed by Avnet.Display: The display adapter board, display panel, touchscreen, and any other components that make up a display kit.

Connector: An unmodified reference to The connector refers to the Avnet Display Interface Connector, specified in thisdocument.Display Adapter: If used standalone, refers to the display adapter board.Interposer: The board that adapts a 3rd party development board to the Avnet Display Interface ConnectorTSC: TouchScreen Controller. A device that interfaces to a touchscreen and provides the measurements of finger or styluslocation.DDC: Display Data Channel. A VESA standard defining a interface bus between a display monitor and video adapter forthe purpose of communicating the functional capabilities of the monitor to the video adapter. Based on I2C.

3 DisclaimerThis document serves as a guideline only. Avnet Inc. reserves the right to make changes to this specification at any timewithout notice. Avnet makes no commitment to provide support for customers designing with this specification.



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4 IntroductionDisplays are used in a wide range of applications. This specification defines a common interconnect standard for Avnedevelopment kits (hosts) and display kits (displays). The purpose of this standard is to allow the hardware connection of anyAvnet development kit with a display interface to any compatible display kit. It leaves the specific aspects of the host anddisplay kit design up to future developers.

There are three components in this interconnect that are covered in this specification: the display connector on both thedevelopment board and the display adapter board, and the cable to connect them. It is worth describing the concept madepossible by this specification. Figure 1 shows a typical development board/display kit configuration, as well as the scope othis specification (in the yellow box).

Avnet Display Kit

Avn

etDisplay

Ada

pterBoard

Display Panel,Backlight, and

Touchscreen

Avnet Display Kit

Avn

etDisplay

Ada

pterBoard


Touchscreen


Touchscreen

Avnet Development BoardAvnet Development Board

RibbonCable

Avnet LCD Interface (ALI)

Figure 1 Typical Avnet Development Board / Display Kit Configuration

This configuration contains an Avnet-designed development board (called a host in this document) that contains severacomponents including a processor, programmable logic device (PLD), or other such device that is capable of driving agraphic display. This board also contains the ALI connector, whose design is specified in this document. The purpose o

the ALI connector is to conduct power and data signals in a specific way to the display adapter board, located in the displaykit itself. A ribbon cable is used to connect the host board to the display adapter board.

The display adapter board, which receives the signals from the development board over the ribbon cable, has the followingpurposes:

Convert the signals from the development board into a format that is compatible with the display. Develop the appropriate power, drawn from either the development board or an externally provided power source to

power the backlight, the display, and any other components which might be necessary.

Provide the necessary physical connections to allow the board to mate to the display, touchscreen, and backlightOften, these physical connections vary from display to display, even within display supplier families.

4.1 Scope of this DocumentThis document defines the electrical and physical specifications for the Avnet LCD Interface, or ALI. Electrically, this meansthe signal definitions, connector pinouts, and optional and mandatory signals (such as power). Also, this defines somebasic voltage and current levels to ensure compatibility. Physically, this specifies the connectors and cables used. Theyellow box in Figure 1 shows the scope of this document.



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4.2 Interface to 3rd party Development BoardsThere are many existing development systems which could potentially mate with Avnet display kits. These systems wimost likely not have the ALI connector on them. An inexpensive interposer board could be designed in order to adapt the3rd party development system to the ALI standard.

Avnet Display Kit

AvnetDisplay

AdapterBoard

AvnetDisplay

AdapterBoard

Display Panel,Backlight, andTouchscreen

Display Panel,Backlight, andTouchscreen

3rd PartyDevelopment Board

RibbonCable

Interposer

Interposer

Figure 2 - Interface to 3rd Party Development Boards, Showing Interposer

4.3 Direct Mating of Hosts and DisplaysThe specification allows for the direct mating of properly-designed ALI-compatible hosts and displays. See the physicaportion of this specification for more details.

Avnet Display Kit

AvnetDisplay

Adapter

Board

AvnetDisplay

Adapter

Board

Display Panel,

Backlight, andTouchscreen

Display Panel,

Backlight, andTouchscreen

Avnet Development Board

DirectMate

4.4 Types of DisplaysThis standard is designed to support TFT LCD graphics display panels. Connections to other types of displays might be

possible, but consideration of this has not been taken into account in this standard.

4.5 Supported Display InterfacesThis standard supports two types of display data interfaces parallel and serial. The specification calls these Parallel ALIand Serial ALI. The only difference between Parallel ALI and Serial ALI is the display data interface. All other featuressuch as the serial busses, touchscreen, control, and power are common between the two.



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4.5.1 Parallel ALIA parallel display interface is one that passes digital pixel data in parallel form, usually in the form of fixed-width RGB (RedGreen, and Blue) format. This specification allows for connection of up to 24-bits of parallel pixel data. Support for loweparallel bus widths is included here as well. Parallel ALI uses 60-pin connector and cable.

4.5.2 Serial ALIThis standard supports serial display interfaces via LVDS (Low Voltage Differential Signaling) of up to 4 data channels, with

an independent clock channel. Serial ALI uses the same 60-pin connector as the parallel ALI.

4.6 Supported Backlight InterfacesSince backlight power is specific to the display and backlight, this standard does not attempt to specify the types obacklights to be supported. Each display tends to have unique power requirements for its backlight and that is left to thedesigner of the display adapter board.

Host-based brightness control of the backlight is enabled by this spec through the use of a single PWM (Pulse WidthModulated) signal.

4.7 Touchscreen InterfacesThis standard supports the physical connection between the host and display of 4 and 5-wire resistive touchscreens. This isused in the case that a host board has a touchscreen controller (TSC) built-in. It is not a requirement for the display kit tocontain, or the host board to support, a touchscreen.

4.8 Serial Communications InterfacesTwo types of serial interfaces are supported to provide low-bit rate serial communication between the host board and thedisplay kit. These are I2C (Inter-Integrated Circuit) interface and SPI (Serial Peripheral Interface). The purpose of theseinterfaces is to allow the control, if necessary, of optional components on the display adapter board from the developmentboard. One primary example of how this might be used is to interface the host to the touchscreen controller (TSC) locatedon the display adapter board. Support for these interfaces by the host and display is optional.

The connection of the I2C interface on the host is encouraged. This would guarantee connectivity to DDC (Display DataChannel) memories on display adapters. Some display manufacturers provide DDC memories on the display itself.

4.9 PowerThis standard sets requirements for the voltages supplied by host. It sets the maximum amount of power that a display kitcan draw from a host. It does not set demands on the amount of current that a host must provide to a display.



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5 Electrical SpecificationThe following section describes the electrical details of this specification, including connector pin-out, provisions for variousmodes of operation, and provisions for optional features (such as the presence of off-board touchscreen controllers).

5.1 Parallel ALI and Serial ALIThere are two connectors specified in order to service both parallel and serial displays. The serial ALI connector onlyprovides a serial interface from the host board to the display. The parallel ALI connector only supports a parallel host boardand a parallel display. The other signals, such as touchscreen, SPI and I2C, display control, and power are commonbetween the two connectors.

Figure 3 shows the I/O and connections on both the serial and parallel ALI connectors. Notice that in the upper part of thediagram, the signaling differs. This pertains to the serial and parallel video display signals. In the lower part of the diagramthe signaling is the same. So, while the serial and parallel interfaces differ, the other signals are common.

ALIC

onnector

44SPI

22I2C

44PWR5V

33PWR33V

1010GND

55

PWM_DIM

RESET_N

TOUCH_x

ON_OFF

SerialDisplay

Interface(LVDS)

DisplayControl

SerialCommunications

AnalogTouchscreen

PowerSupply

22

22

22

22

22

SERIAL_D0+/-

SERIAL_D1+/-

SERIAL_D2+/-

SERIAL_D3+/-

SERIAL_CLK+/-

ALIC

onnector

88R[0..7]

88G[0..7]

88B[0..7]

HSYNC

VSYNC

CLK

DE

44SPI

22I2C

44PWR5V

33PWR33V

1010GND

55

PWM_DIM

RESET_N

TOUCH_x

ON_OFF

ParallelDisplay

Interface(3.3V LVCMOS)

DisplayControl

SerialCommunications

AnalogTouchscreen

PowerSupply

Serial Parallel

IRQ_N IRQ_N

Figure 3 Serial and Parallel ALI Connector I/O (Host Side)



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5.2 Interface Signal TableTable 1 lists all of the interface signals, signal type, and description. For an explanation of signal type, see the definitionsafter the table.

Table 1 - Interface Signal List

Group Signal Name Type DescriptionParallel ALI R0 R7 Out, SE, LVCMOS Parallel red data bus bits 0 through 7. Bit 7 is the MSB. Synchronized to CLK.

Parallel ALI G0 G7 Out, SE, LVCMOS Parallel green data bus bits 0 through 7. Bit 7 is the MSB. Synchronized to CLK.Parallel ALI B0 B7 Out, SE, LVCMOS Parallel blue data bus bits 0 through 7. Bit 7 is the MSB. Synchronized to CLK.

Parallel ALI HSYNC Out, SE, LVCMOS Horizontal synchronizing signal for parallel video interface. Synchronized to CLK.

Parallel ALI VSYNC Out, SE, LVCMOS Vertical synchronizing signal for parallel video interface. Synchronized to CLK.

Parallel ALI CLK Out, SE, LVCMOS Data Clock. Synchronizes all signals in the parallel ALI.

Parallel ALI DE Out, SE, LVCMOS Data Enable. Used by some displays to indicate valid data and syncs.

Serial ALI SERIAL_D0 toSERIAL_D3

Out, Diff, LVDS Serial LVDS Data Channels 0 though 3 (differential). Contains the serialized color andcontrol data for the display. Data is synchronized to SERIAL_CLK.

Serial ALI SERIAL_CLK Out, Diff, LVDS High-speed serial LVDS clock (differential). Synchronizes SERIAL_DO throughSERIAL_D3.

I2C bus I2C_SDA Bidir, SE, OD Open-drain bidirectional I2C data signal. In normal I2C communications, this signal willbe driven low by both the master (typically the host) and the slave (the display).

I2C bus I2C_SCL Bidir, SE, OD Open-drain bidirectional I2C clock signal. Only driven by the I2C master.

SPI Bus SPI_MISO In, SE, LVCMOS SPI Master In Slave Out (MISO). SPI serial data driven from the slave (the display) tothe master (the host). Synchronized to the SPI_SCLK.

SPI Bus SPI_MOSI Out, SE, LVCMOS SPI Master Out Slave In (MOSI). SPI serial data driven from the master (the host) to thslave (the display). Synchronized to the SPI_SCLK signal.

SPI Bus SPI_SCLK Out, SE, LVCMOS SPI Serial Clock. Clock signal driven by the SPI master (the host) which clocks data intand out of the slave via the MISO and MOSI data signals.

SPI Bus SPI_SSELECT Out, SE, LVCMOS SPI Slave Select. Active high signal driven by the SPI master (the host) to select theslave for communication. Allows multiple slaves to communicate with a single master.The display adapter can only have 1 SPI slave.

Touchscreen TOUCH_XR Passive Touchscreen, X right. For four-wire resistive touchscreens, this is the right X-axiselectrode. For 5-wire touchscreens, this is the upper right corner electrode.

Touchscreen TOUCH_XL Passive Touchscreen, X left. For four-wire resistive touchscreens, this is the left X-axiselectrode. For 5-wire touchscreens, this is the upper left corner electrode.

Touchscreen TOUCH_YT Passive Touchscreen, Y top. For four-wire resistive touchscreens, this is the upper (or top) Y-axelectrode. For 5-wire touchscreens, this is the lower right corner electrode.

Touchscreen TOUCH_YB Passive Touchscreen, Y bottom. For four-wire resistive touchscreens, this is the lower (orbottom) Y-axis electrode. For 5-wire touchscreens, this is the lower left corner electrod

Touchscreen TOUCH_WIPER Passive Wiper signal used in 5-wire resistive touchscreens.

Display Control IRQ_N In, SE, LVCMOS Interrupt request from on-board electronics, such as touchscreen controllers.

Display Control RESET_N Out, SE, LVCMOS Reset, Active Low. Driven by the host as a master warm reset of all display electronics

Display Control ENABLE Out, SE, LVCMOS Display On/Off.

Display Control PWM_DIM Out, SE, LVCMOS PWM Backlight Dimming Control

Power PWR5V Power Power, +5V

Power PWR33V Power Power, +3.3V

Power PWRBL Power Backlight Power. If power is available on the host for driving a backlight,

Power GND Power Ground, Return

Signal Type Abbreviations:Out: Driven by the host. Input to the display.In: Driven by the display. Input to the host.Bidir: Bidirectional. Can be driven by both the host and the display.SE: Short for Single-ended. Only one conductor required per signal. Signal level is referenced to ground.Diff: Short for Differential. Signal level determined by the difference between two signals. Requires a pair of conductors.LVCMOS: Low-Voltage CMOS. CMOS signals for 3.3V logic.Passive: Connects to a resistive or capacitive element on the display (such as a touchscreen). Not driven by the display.Power: Power supply voltage or ground.



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5.3 Interface PinoutFigure 4 shows a top view of both the parallel and serial connectors.

Parallel ALI

R1

G1

DE

SPI_MOSI SPI_SSELECT

HSYNC

TOUCH_XL

TOUCH_YB

TOUCH_WIPER

1 2

3 4

5 6

7 8

9 10

11 12

14

15 16

13

17 18

20

21 22

19

23 24

26

27 28

25

29 30

32

33 34

31

35 36

37 38

40

41 42

39

43 44

45 46

48

49 50

47

51 52

53 54

55 56

58

59 60

57

1 2

3 4

5 6

7 8

9 10

11 12

14

15 16

13

17 18

20

21 22

19

23 24

26

27 28

25

29 30

32

33 34

31

35 36

37 38

40

41 42

39

43 44

45 46

48

49 50

47

51 52

53 54

55 56

58

59 60

57

R0

R2

R4

R6

GND

G0

G2

G4

G6

GND

B0

B2

B4

B6

GND

PWR33V

GND

PWR33V

PWR5V

I2C_SCL

SPI_MISO

SPI_SCLK

VSYNC

R3

R5

R7

G3

G5

G7

GND

B1

B3

B5

B7

GND

GND

PWR5V

PWR33V

GND

IRQ_N

PWR5VI2C_SDA

PWM_DIM

CLK

TOUCH_XR

TOUCH_YT

ON_OFF

RESET_N

GND

GND

PWR5V

Serial ALI


TOUCH_XL

TOUCH_YB

TOUCH_WIPER

1 2

3 4

5 6

7 8

9 10

11 12

14

15 16

13

17 18

20

21 22

19

23 24

26

27 28

25

29 30

32

33 34

31

35 36

37 38

40

41 42

39

43 44

45 46

48

49 50

47

51 52

53 54

55 56

58

59 60

57

1 2

3 4

5 6

7 8

9 10

11 12

14

15 16

13

17 18

20

21 22

19

23 24

26

27 28

25

29 30

32

33 34

31

35 36

37 38

40

41 42

39

43 44

45 46

48

49 50

47

51 52

53 54

55 56

58

59 60

57

GND

GND

PWR33V

PWR33V

PWR5V

I2C_SCL

SPI_MISO

SPI_SCLK

GND

GND

PWR5V

PWR33V

GND

IRQ_N

PWR5VI2C_SDA

PWM_DIM

TOUCH_XR

TOUCH_YT

ON_OFF

RESET_N

GND

GND

PWR5V

SERIAL_D0_NSERIAL_D0_P



SERIAL_D3_N

SERIAL_CLK_N

SERIAL_D3_P

SERIAL_CLK_P

GND

GND

GND

Figure 4 - Parallel and Serial ALI Host Connector Pin-out, Top View



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5.4 Connector InterfacesThis section discusses the electrical details of the different ALI signals. They are grouped by interface.

5.4.1 Display Interface: ParallelThe parallel display interface supports parallel pixel data at up to 8 bits per color component (typically R, G, and B) for atotal data bus width of 24 bits. The signals comprising the parallel display interface are the color buses (R0 through R7, G0through G7, and B0 through B7), HSYNC, VSYNC, DE, and CLK.

5.4.1.1 Voltage LevelsThe ALI requires that these signals be at 3.3V LVCMOS voltage levels as they enter the host ALI connector.

5.4.1.2 Signal DriveIn order to mitigate signal integrity issues, these signals must be driven by a strong bus driver with symmetrical output driveSuch a driver will sink and source equal amounts of current at high and low levels. This ensures that the output impedanceof the driver is equal in the high state and in the low state. Strong drive capability ensures that the output impedance will besuitably low, allowing for a series termination of the line.

Table 2 LVCMOS33 Signal Specifications for Parallel Video Bus (Parallel ALI Only)

Quantity Min MaxOutput Voltage, High state(VOH) 2.8V 3.3V

Output Voltage, Low state (VOL) 0V 0.4V

Output Current Drive +/-24mA -

5.4.1.3 TerminationThis spec calls for using an unshielded ribbon cable to carry signals between the host and the display. In order to minimizereflections, proper termination should be used on all single-ended signals with higher rise/fall times. These include all of theparallel display interface signals (R, G, B, HSYNC, VSYNC, DE, and CLK).

The cable has a characteristic impedance of 105 ohms and will add approximately 20pf of load capacitance. In many casesprocessors and FPGAs may not be able to adequately drive this level of impedance. Also, the output impedance of thedisplay interface on the host may not be made to easily match the transmission line impedance with a series termination. Inthis case, a line driver IC with decent output drive, such as the 74LCX244 from Fairchild, should be used to drive the single-ended high-speed signals.

Host Display

Output

Line Driver Z

IC

Ex: 74LCX244

RS Input

Buffer

Output Impedance = RO Input Impedance =

To minimize reflections: RO

+RS

= Z

Figure 5 Using a 74LCX244 to Drive the Line

In the case of the 74LCX244, the output impedance can be approximated by dividing the low output voltage (V OL) by thecurrent (IOL). VOL = 0.55V for an IOL = 24mA. RO ~ VOL/IOL ~ 22 ohms. RS would need to be 83 ohms to series terminatethis line.

5.4.1.4 Support for Smaller-Width BussesMany displays and hosts will only support smaller bus widths. In this case, the MSB of the color bus from the video sourceis mapped into the MSB of the connector. In a simple example, suppose a host is only capable of supporting an 18-bit bus(6 bits per color) is connected to a 24-bit display. In this case the MSB (bit 5) of each color component bus is mapped into



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bit 7 of the corresponding color bus on the connector. The least-significant two bits of the connectors color bus are eithedriven low or pulled down to ensure that a low voltage is presented to the display on these bits.

There are cases where a host can support a full 24-bit output bus, while the display will only support a smaller input bus. Inthis case, the display maps the MSB of each color component from the ALI connector (R, G, and B) into the correspondingMSB of each color bus.

Table 1 shows an example of how an 18-bit host connects through the display interface connector into display.

Table 3 - Example: Mapping an 18-bit host into an 18-bit display through the connector

Host Video Bus (18-bitoutput, 6 bits per color)

ALI Connector Signal (24bits, 8 bits per color)

Display Video Bus (18-bitinput, 6 bits per color)

Bit 5 Maps to Bit 7 Maps to Bit 5






None pull down or drive low Maps to Bit 1 Maps to No Connect

None pull down or drive low Maps to Bit 0 Maps to No Connect

5.4.1.5 Support for Asymmetric Color ComponentsConnecting to 16-bit color interfaces is necessary in many cases. Since having the same width color is impossible inexactly 16-bits, many displays and processors will support a convention called RGB565. In RGB565, there are 16-bits ocolor information: 5 bits for red, 6 bits for green, and 5 bits for blue. The total adds up to 16 bits. This would map into theALI connector the same way as a symmetric color bus would. The MSB for the red, green, and blue busses would map intobit 7. In the case of red and blue, this is bit 4. In the case of green, this is bit 5.

Table 4 Parallel ALI Color Bus Showing Various Modes

Signal Name Description RGB565 Displays RGB666 Displays RGB888 Displays

R0 Red Data Bit 0 Not used, pull down Not used, pull down R0R1 Red Data Bit 1 Not used, pull down Not used, pull down R1

R2 Red Data Bit 2 Not used, pull down R0 R2

R3 Red Data Bit 3 R0 R1 R3





G0 Green Data Bit 0 Not used, pull down Not used, pull down G0

G1 Green Data Bit 1 Not used, pull down Not used, pull down G1

G2 Green Data Bit 2 G0 G0 G2G3 Green Data Bit 3 G1 G1 G3

G4 Green Data Bit 4 G2 G2 G4




B0 Blue Data Bit 0 Not used, pull down Not used, pull down B0

B1 Blue Data Bit 1 Not used, pull down Not used, pull down B1

B2 Blue Data Bit 2 Not used, pull down B0 B2

B3 Blue Data Bit 3 B0 B1 B3




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5.4.2 Display Interface: SerialFor serial display interfaces, there is support for up to 4 high-speed differential serial channels (SERIAL_Dx), and a high-speed serial clock (SERIAL_CLK).

Each signal is an LVDS pair, requiring two pins. The color data and syncs are serialized across multiple lanes. Theparticular way these are serialized is dependent on the display itself. This specification only stipulates locations of the fousignal pairs to be used, their polarity, and other electrical specifications.

5.4.2.1 Signal Levels and CouplingThe LVDS signal pairs will adhere to the following specifications as they leave the host board. They are not to be ACcoupled.

Table 5 LVDS Signal Specifications (Serial ALI Only)

Quantity Min MaxDifferential Voltage +/- 250 mV +/- 450 mV

Common Mode Voltage 1.13V 1.38V

5.4.2.2 TerminationIn this specification there is only one driver and one receiver for each LVDS signal, creating a point-to-point connection.The recommended way of terminating LVDS is to use a resistor of 90 to 110 ohms across the input of the LVDS receiver,for a 100 ohm impedance transmission line.

Z

For proper termination: RT = Z

RT

Figure 6 - LVDS Point-to-Point Termination

In many cases the display panel itself will contain the LVDS receiver and termination resistor. In the event that thetermination resistor is not present, one should be added on the display adapter board and it should be situated as close aspossible to the display data connector. No termination is necessary on the host board.

Both signals of channel 4 (SERIAL_D4) should be connected to ground with 10Kohm resistor on the host board. This wilprevent floating signals in cases where only three channels are required by the display.

5.4.3 I2CI2C consists of 2 signals, I2C_SDA and I2C_SCL. These are bidirectional, open-drain signals. They must be pulled up onthe host to PWR33V using 1.1Kohm or greater resistors. They must not be pulled up on the display.

5.4.3.1 Terminating Unused I2C SignalsIf unused on the host, the I2C signals should be pulled up to PWR33V. If unused on the display, the I2C signals should beleft unconnected.



14/20


Table 6 - I2C Bus Termination

Case Host Display AdapterUsed Pull-up to PWR33V using 1.5Kohms Direct connect to I2C devices

Unused Pull-up to PWR33V using 1.5Kohms Leave unconnected

5.4.3.2 Devices Requiring I2C Bus Voltages Greater than 3.3VIf I2C signal voltages higher than PWR33V are required at the display, then an I2C bus translator such as the TI P82B715

can be used on the display adapter.

PWR33V

Lx

Ly

PWR33V

I2C_SCL

I2C_SDA

Lx

Ly

PWR33V

I2C_SCL

I2C_SDA

Sx

Sy

+5V

LOCAL SDA

LOCAL SCLSx

Sy

+5V

LOCAL SDA

LOCAL SCL

P82B715

To/From

Avnet Display

Connector

To/From

Local +5V

I2C Interface

Figure 7 - Example of I2C Voltage Translation (Display Adapter Side)

5.4.4 SPISPI consists of four signals: SPI_MOSI, SPI_MISO, SPI_SCLK, and SPI_SSELECT. These are all unidirectional signalsSPI is a master-slave interface. In the case of this specification, the master is the host and the slave is the displayTherefore, SPI_MOSI, SPI_SCLK, and SPI_SSELECT are outputs from the host to the display, and SPI_MISO is an outpufrom the display to the host.

All SPI signals are push-pull outputs that must adhere to LVCMOS signal levels. If signal levels higher than PWR33V arerequired on the display, then a voltage level translator should be used on the display adapter board.

All SPI signals must be pulled down to GND using 10Kohm resistors. This is to prevent floating input voltages in the casethat the SPI signals are unused on either the host or the display.

5.4.4.1 Terminating Unused SPI SignalsIf a display does not use the SPI signals, it should leave them unconnected. A host should pull-up the signals on theconnector regardless of whether it provides actual SPI to the connector.

Table 7 - SPI Bus Termination

Case Host Display AdapterUsed Pull-down using 10Kohms Direct connect to SPI devices.

Unused Pull-down using 10Kohms Leave unconnected

5.4.5 Display Control SignalsThere are four signals classified as Display Control. Outputs from the host to the display are ON_OFF, PWM_DIM, andRESET_N. The host can optionally drive these signals. There is a single output from the display to the host called IRQ_NThese must be LVCMOS (3.3V) level signals.

ON_OFF is an active high signal that serves as an ON/OFF control for the display backlight, useful in power-sensitiveapplications, and sequencing the backlight on and off to prevent the user from seeing initialization artifacts. This signamust be pulled up to 3.3V on the host using a weak pull-up (10K or greater).



15/20


PWM_DIM allows programmable dimming control of the display backlight. The actual frequency and duty are backlightspecific and are not specified here. This is an LVCMOS push-pull signal output from the host. This signal must be pulledup to 3.3V on the host using a weak pull-up (10K or greater).

RESET_N is an active-low reset signal driven from the host to the display. This signal allows the host to reset the displayelectronics. This signal must be pulled up to 3.3V on the host using a weak pull-up (10K or greater).

IRQ_N is an active-low interrupt request signal driven from electronics on the display adapter such as touchscreen

controllers. This signal should be pulled up on the display adapter using a weak pull-up (10K or greater).Table 8 PWM_DIM, ON_OFF, RESET_N, IRQ_N Signal Termination

Case Host Display AdapterUsed Pull-up to PWR33V using 10Kohms Direct connect to appropriate devices.

Unused Pull-up to PWR33V using 10Kohms Leave unconnected

5.4.6 Touchscreen SignalsThere is support for both 4 and 5 wire resistive touchscreens. These are via the TOUCH_XL, TOUCH_XR, TOUCH_YLTOUCH_YR, and TOUCH_WIPER signals. These signals are completely passive and are to be connected directly toresistive touchscreens.

5.4.6.1 Simultaneous Support for both Host and Display Adapter-based Touchscreen Controller (TSC)For flexibility, either the host or the display adapter may contain an on-board TSC. The TOUCH_x signals are used by thehost if host board contains a compatible TSC. The TOUCH_x signals would not be used by the host if the host-based TSCis incompatible with the touchscreen on the display or if the host board contains no TSC, and therefore requires an externaTSC. In order for most hosts to make use of a touchscreen the designer of any display adapter should seriously considerdesigning a SPI or I2C-based TSC onto the board.

If a display adapter contains an on-board touchscreen controller (TSC) there must be a method for connecting thetouchscreen signals to either the TSC or to the TOUCH_x signal lines on the ALI cable, and not both at the same time.There are two reasons for this. In the first case, that of a host which does not have an on-board touchscreen controller

Noise coupled onto the unused TOUCH_x signal lines may corrupt the TSC measurements. In the second case, the hosdoes have a touchscreen controller and the display adapter-based TSC will simultaneously drive the same touchscreensignals.

Figure 8 illustrates two suggested ways to isolate the touchscreen signals. To minimize the number of jumpers, the firsmethod employs a low RON analog switch. The second method is the simplest, making use of either four or five three-pinjumpers. The number of required jumpers or switches corresponds to the number of touchscreen wires. This specificationsupports the use of either.



16/20


Low

RONAnalog

Switch

Touchscreen

ControllerA

B

YALI

Connector

Touchscreen

Connector

Sel

A or B

Select

Jumper

To Host Board

I2C

or

SPI

Analog Touchscreen Signals

(TOUCH_x)

Touchscreen

Controller

ALI

Connector

Touchscreen

Connector

To Host Board

I2C

or

SPI


(TOUCH_x) x4 or x5

3-pin

Jumpers

Figure 8 - Two Methods to Prevent Simultaneous Connection of Touchscreen Signals

5.4.6.2 Terminating Unused TOUCH_x SignalsIn the event that the touchscreen signals are not used by the host, they should be terminated with a 100ohm pull-downresistor to board ground. This sinks coupled noise on the touch signals to ground and will not corrupt display-based TSCmeasurements due to the isolation scheme required above. If they are unused by the display, in case the display does nohave a resistive touchscreen, they should be terminated with a 10k pull-down resistor on the display adapter. This preventsthe signal lines from floating and collecting noise in case the host has an on-board TSC.

Table 9 - TOUCH_x (Resistive Touchscreen) Termination

Case Host Display AdapterUsed Direct connect to on-

board TSCConnect through A/B switch totouchscreen

Unused Connect to GND through100ohms Connect to GND through10Kohms

ALI

Connector


(TOUCH_x)

Host Board Display Board

10KOhms

without TSCwithout TSC

ALI

Connector


(TOUCH_x)

100 Ohms

Figure 9 Termination of Unused TOUCH_x Signals on the Host Board and Display Board

5.5 PowerThere are several power sources supplied by the host to the display. These are +3.3V and +5V. The host must supply+3.3V and +5V. These required supplies are used by the display adapter board to generate the supply voltages for thecomponents of the display kit including the display panel, touchscreen, and backlight.



17/20


5.5.1 3.3V Power (PWR33V)The maximum current that can be drawn from the 3.3V bus by a display is 0.650 Amps. This is based on the 75% deratedmaximum current handling capability of 3 28AWG wires that provide 3.3V to the display from the host. This does not dictatethe amount of current that the host must provide, but is a guideline for host board development and should accommodatethe power requirements for a large set of LCD panels.

5.5.2 5V Power (PWR5V)The maximum current that can be drawn from the 5V bus is 0.850 Amp. This is based on the 75% derated maximumcurrent handling capability of the 4 28AWG wires that provide 5V to the display from the host. This does not dictate theamount of current that the host can provide at 5V, but is a guideline for development.

If this supply is not used by the display, it should be physically no-connected on the display adapter board.

5.5.3 Use of an External Power SupplyIf a display requires more power than the host can provide, either due to a host power supply limitation or the currenlimitation provided in this specification, an auxiliary external supply may be used to provide the appropriate power to thedisplay. This should be provided on the display adapter itself.

In this case, unused supplies sourced from the host should be physically disconnected on the display adapter. However alground pins must still be connected (to avoid floating ground mismatch).

5.6 Parallel ALI ExampleThe following diagram shows connection examples Parallel ALI. Note the pull-ups, pull-downs, and line drivers. Thisexample shows the use of a SPI-based touchscreen controller (TSC) on the display adapter.

Line DriverIC

ex:74LCX16244

88R[0..7]

88G[0..7]

88B[0..7]

HSYNC

VSYNC

CLK

DE

22I2C

44SPI

44PWR5V33PWR33V

1010GND

55

RESET_N,

PWM_DIM,

ON_OFF,

IRQ_N

Host Display

Output

(Processor or

FPGA)

Line Driver

IC

ex:74LCX16244

RS = 83ohms

Output Impedance ~ 22ohms

TOUCH_x

PWR33V

Power Supply5V @ 860mA

3.3V @ 680A

10Kohms

10Kohms

44

PWR33V

1.5Kohms

Parallel ALI Host Parallel ALI Display Adapter

88

88

88

R[0..7]

G[0..7]

B[0..7]

HSYNC

VSYNC

CLK

DE

22 I2C

44 PWR5V

33 PWR33V

RESET_N

DisplayPanel

Connector

ON/OFF

1010 GND

On Board

Power

PWM_DIM

Resist.

Touchscreen

TOUCH_x55

Backlight

Connector

Backlight

Supply

44 SPIALIDisplayConnector

ALIHostConnector

SPI

Touchscreen

Controller

4 or 5IRQ_N

Figure 10 Parallel ALI Host and Display Adapter Example (with SPI-based TSC)



18/20


5.7 Serial ALI ExampleExamples of a serial ALI host and display are shown in the following diagram. In this case the display adapter has an I2Cbased TSC on-board. Notice the pull-ups and pull-downs.

ALIHostConnectorHost Display

Output

(Processor or

FPGA)

Power Supply

5V @ 860A

3.3V @ 680A

22

22

22

22

22

SERIAL_D0

SERIAL_D1

SERIAL_D2

SERIAL_D3

SERIAL_CLK

22I2C

44SPI

44PWR5V

33PWR33V

1010GND

55

RESET_N,

PWM_DIM,

ON_OFF,

IRQ_N

TOUCH_x

PWR33V

10Kohms

10Kohms

44

PWR33V

1.5Kohms

10Kohms

Serial ALI Host

ALIDisplayConnector

22 I2C

44 PWR5V

33 PWR33V

RESET_N

Display

Panel

Connector

ON/OFF

22

22

22

22

22

1010 GND

On Board

Power

I2C

Touchscreen

Controller

PWM_DIM

Resist.

Touchscreen

4 or 5

TOUCH_x55

Backlight

Connector

Backlight

Supply

44 SPI

SERIAL_D0

SERIAL_D1

SERIAL_D2

SERIAL_D3

SERIAL_CLK

Serial ALI Display Adapter

IRQ_N

Figure 11 Serial ALI Host and Display Adapter Example (with I2C-based TSC)

6 Physical SpecificationThis section defines the type of connectors and ribbon cables to be used.

6.1 ConnectorThe same connectors are used on both the host and the display. Compatible connector part numbers and manufacturersare listed here in Table 10. Figure 12 is a picture of a smaller version of this connector.

Figure 12 - Picture of Tyco AMP-LATCH Type Header and 3M Receptacle

The connectors are inexpensive and polarized to prevent improper plugging.

Table 10 - ALI Connector Compatible Part Numbers

Connector Type Location Manufacturer Part NumberTyco Electronics/AMP 1-103308-2Shrouded Header, 0.100 x 0.100 centerline,

60 pins, with polarizationALI Host and Display

Molex 0702466001

0.100 x 0.100 polarized boardmountreceptacle, 60 pins

ALI Display (instacked configuration)

3M 8560-4500PL



19/20


6.1.1 Host / Display Direct Connection (Stacked Configuration)To allow for direct connection of a host board and a display in a stacking configuration, the host connector must be mountedon the top side of the host board and a female display connector (i.e. the boardmount receptacle in Table 10) must bemounted on the bottom side of the display adapter board.

Display

Display Adapter Board

Host Board

Figure 13 Direct Stacking of Display and Host Board

6.1.2 Connector Pin-out Mirroring (Stacked Connection)In this configuration, the display ALI connector pin-out is mirrored when viewed from the top of the connector. This can beconfusing, and special care is needed. To better illustrate this, Figure 14 shows the pin-out of the parallel ALI connectorsfor both the host and the display.

Parallel ALI Host and Display(Top View)

Parallel ALI Display(Bottom View)

Parallel ALI Display(Top View)

1 2

3 4

5 6

7 8

9 10

11 12

14

15 16

13

17 18

20

21 22

19

23 24

26

27 28

25

29 30

32

33 34

31

35 36

37 38

40

41 42

39

43 44

45 46

48

49 50

47

51 52

53 54

55 56

58

59 60

57

1 2

3 4

5 6

7 8

9 10

11 12

14

15 16

13

17 18

20

21 22

19

23 24

26

27 28

25

29 30

32

33 34

31

35 36

37 38

40

41 42

39

43 44

45 46

48

49 50

47

51 52

53 54

55 56

58

59 60

57

12

34

56

78

910

1112

14

1516

13

1718

20

2122

19

2324

26

2728

25

2930

32

3334

31

3536

3738

40

4142

39

4344

4546

48

4950

47

5152

5354

5556

58

5960

57

12

34

56

78

910

1112

14

1516

13

1718

20

2122

19

2324

26

2728

25

2930

32

3334

31

3536

3738

40

4142

39

4344

4546

48

4950

47

5152

5354

5556

58

5960

57

R1

G1

DE


HSYNC

TOUCH_XL

TOUCH_YB

TOUCH_WIPER

1 2

3 4

5 6

7 8

9 10

11 12

1415 1613

17 18

20

21 22

19

23 24

26

27 28

25

29 30

32

33 34

31

35 36

37 38

40

41 42

39

43 44

45 46

4849 5047

51 52

53 54

55 56

58

59 60

57

1 2

3 4

5 6

7 8

9 10

11 12

1415 1613

17 18

20

21 22

19

23 24

26

27 28

25

29 30

32

33 34

31

35 36

37 38

40

41 42

39

43 44

45 46

4849 5047

51 52

53 54

55 56

58

59 60

57

R0

R2

R4

R6

GND

G0

G2

G4

G6

GND

B0

B2

B4

B6

GND

PWR33V

GND

PWR33V

PWR5V

I2C_SCL

SPI_MISO

SPI_SCLK

VSYNC

R3

R5

R7

G3

G5

G7

GND

B1

B3

B5

B7

GND

GND

PWR5V

PWR33V

GND

IRQ_N

PWR5VI2C_SDA

PWM_DIM

CLK

TOUCH_XR

TOUCH_YT

ON_OFF

RESET_N

GND

GND

PWR5V

DE

SPI_MOSI

HSYNC

R0

R2

R4

R6

G0

G2

G4

G6

GND

B0

B2

B4

B6

I2C_SCL

SPI_MISO

SPI_SCLK

VSYNC

IRQ_N

I2C_SDA

PWM_DIM

CLK

TOUCH_XR

TOUCH_YT

ON_OFF

RESET_N

GND

GND

R1

G1

SPI_SSELECT

TOUCH_XL

TOUCH_YB

TOUCH_WIPER

GND

GND

PWR33V

GND

PWR33V

PWR5V

R3

R5

R7

G3

G5

G7

GND

B1

B3

B5

B7

GND

GND

PWR5V

PWR33V

GND

PWR5V

PWR5V

R1

G1

SPI_SSELECT

TOUCH_XL

TOUCH_YB

TOUCH_WIPER

GND

GND

PWR33V

GND

PWR33V

PWR5V

R3

R5

R7

G3

G5

G7

GND

B1

B3

B5

B7

GND

GND

PWR5V

PWR33V

GND

PWR5V

PWR5V

DE

SPI_MOSI

HSYNC

R0

R2

R4

R6

G0

G2

G4

G6

GND

B0

B2

B4

B6

I2C_SCL

SPI_MISO

SPI_SCLK

VSYNC

IRQ_N

I2C_SDA

PWM_DIM

CLK

TOUCH_XR

TOUCH_YT

ON_OFF

RESET_N

GND

GND

Header Connector Socket Connector (Stacking Display Configuration)

Figure 14 Parallel ALI Pin-out for Host and Display (Top and Bottom views)



20/20


6.1.3 Silkscreen Identification of Parallel and Serial ALIThe same connector is used for both serial and parallel ALI. In order the prevent confusion these shall be clearly marked onboth the host and display PCBs, as near the connectors as possible, using silkscreen. The marking for parallel ALI isParallel ALI or Parallel Avnet LCD Interface and for serial ALI it is Serial ALI or Serial Avnet LCD Interface."

6.2 CableThe connection between the host and display connectors is designed to work with any 0.050in pitch standard flat ribbon

cable. This cable must have polarized 60-pin 0.100 x0.100 in. female receptacles on both ends. The conductors must mapfrom pin 1 to pin 1. The maximum supported length of this cable is 18 inches, however shorter cables are acceptable. Thesupported wire gauge of each conductor is no less than 0.0028. This cable must exhibit a characteristic impedance of 100+/- 10% ohms. The Serial ALI setup is identical to the Parallel ALI.

Display

Display Adapter BoardHost Board

Cable

Figure 15 Cabled Connection of Display and Host BoardThe layout of the host and display circuit boards should orient the cable connectors so that no twist is required to mateAlso, if the connectors on terminated on opposite faces of the flat cable, they should easily mate without doubling back thecable.

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