AXI HDMI TX

The AXI HDMI TX IP core can be used to interface the ADV7511 and ADV7123 devices using an FPGA.

Features

• AXI based configuration

• Supports multiple resolution (max 1080p)

• Video transmission on 36/24/16 bits or 8 bits RGB

• Supports embedded sync (16bit data)

• YCbCr or RGB color space output

• Data clipping (min. and max. for each chroma/color value)

• Supports Xilinx 7 Series and Ultrascale devices.

• Supports Altera 5 Series SoC

Files

Name	Description
library/axi_hdmi_tx/axi_hdmi_tx.v	Verilog source for the peripheral.

Block Diagram

Configuration Parameters

Name	Description
ID	Core ID should be unique for each axi_hdmi_tx IP in the system.
FPGA_TECHNOLOGY	Used to select the FPGA Technolgy; beyond the “Choices/Range” listed, also supports Altera 5 series (101) devices.
CR_CB_N	Used in the chroma subsampling process, selecting which of the red or blue data components will be transmitted first in-between green samples. 1 = red, 0 = blue
INTERFACE	Interface type towards the 7511. Available options: 16_BIT, 24_BIT, 36_BIT, 16_BIT_EMBEDDED_SYNC, VGA_INTERFACE
OUT_CLK_POLARITY	0 = Launch on rising edge, 1 = Launch on falling edge.

Interfaces

Name	Description
reference_clk	Pixel clock, generated by an axi_clkgen IP core (axi_hdmi_clkgen in reference design.
hdmi_out_clk	Output clock.
s_axis	DMA AXIS interface (vdma).
hdmi_16_hsync	Horizontal sync signal.
hdmi_16_vsync	Vertical sync signal.
hdmi_16_data_e	Data enable signal.
hdmi_16_data	HDMI data.
hdmi_16_es_data	HDMI embedded sync data.
hdmi_24_hsync	Horizontal sync signal.
hdmi_24_vsync	Vertical sync signal.
hdmi_24_data_e	Data enable signal.
hdmi_24_data	HDMI data.
hdmi_36_hsync	Horizontal sync signal.
hdmi_36_vsync	Vertical sync signal.
hdmi_36_data_e	Data enable signal.
hdmi_36_data	HDMI data.
vga_out_clk	Output clock.
vga_hsync	Horizontal sync signal.
vga_vsync	Vertical sync signal.
vga_red	VGA red data.
vga_green	VGA green data.
vga_blue	VGA red data.

Detailed description

The top module (axi_hdmi_tx), instantiates:

• axi_hdmi_tx_core module

• axi_hdmi_tx_vdma module

• the HDMI TX register map

• the AXI handling interface

In axi_hdmi_tx_core module the video information is manipulated by passing through several processing blocks (see Block Diagram):

• CSC (Color Space Converter) –converts the video information from RGB color space to YCbCr color space. If RGB is the desired output color space the CSC block can be bypassed by setting to 1 the value of CSC_BYPASS register.

• Data Clipping bloc gives the possibility of limiting the minimum and maximum color range values. This block is controlled by FULL_RANGE, CLIPP_MAX and CLIPP_MIN registers.

• Chroma subsampling block as its name suggests, samples the video information to obtain a video information that requires less bandwidth and has a minimum impact on the video quality experienced by human eyes.

• Embedded Sync module interleaves the video synchronization signals with the video information, obtaining a more compact transmission path.

• Sync Signals block is responsible for generating the video synchronization signals for video resolutions written in HDMI interface Control register.

The axi_hdmi_tx_vdma module ensures the clock domain crossing circuit between the video source, typically a AXI DMAC core and the axi_hdmi_core, which works at different clock speeds depending on the required resolution.

Register Map

HDMI Transmit (axi_hdmi_tx) register map

Address		Reg Name
HDL	DWORD	BITS	Field Name	Type	Default Value	Description
0x10	0x40	RSTN_TX				HDMI Interface Control & Status
		[0]	RSTN	RW	0x0	Reset, a common reset is used for all the interface modules, The default is reset (0x0), software must write 0x1 to bring up the core.
0x11	0x44	CNTRL1				HDMI Interface Control & Status
		[2]	SS_BYPASS	RW	0x0	If set (0x1) bypasses the chroma sub-sampler. This is primarily intended to be used to send the test-pattern directly to the HDMI transmitter without modifying it.
		[1]	RESERVED	RO	0x0	Reserved
		[0]	CSC_BYPASS	RW	0x0	If set (0x1) bypasses color space conversion (if equipped). And depending on its value, the default value of color space boundaries is set in the CLIPP_MAX and CLIPP_MIN registers.
0x12	0x48	CNTRL2				HDMI Interface Control & Status
		[1:0]	SOURCE_SEL	RW	0x0	Select the HDMI data source- register constant (0x3), incr-pattern (0x2), input (0x1) or disabled (0x0).
0x13	0x4c	CNTRL3				HDMI Interface Control & Status
		[23:0]	CONST_RGB	RW	0x000000	This is the RGB value transmitted, if the source is constant (see above).
0x15	0x54	CLK_FREQ_TX				HDMI Interface Control & Status
		[31:0]	CLK_FREQ	RO	0x00000000	Interface clock frequency. This is relative to the processor clock and in many cases is 100MHz. The number is represented as unsigned 16.16 format. Assuming a 100MHz processor clock the minimum is 1.523kHz and maximum is 6.554THz. The actual interface clock is CLK_FREQ * CLK_RATIO (see below). Note that the actual sampling clock may not be the same as the interface clock- software must consider device specific implementation parameters to calculate the final sampling clock.
0x16	0x58	CLK_RATIO_TX				HDMI Interface Control & Status
		[31:0]	CLK_RATIO	RO	0x00000000	Interface clock ratio - as a factor actual received clock. This is implementation specific and depends on any serial to parallel conversion and interface type (ddr/sdr/qdr).
0x17	0x5c	STATUS				ADC Interface Control & Status
		[0]	STATUS	RO	0x0	Interface status, if set indicates no errors. If not set, there are errors, software may try resetting the cores.
0x18	0x60	VDMA_STATUS_TX				HDMI Interface Control & Status
		[1]	VDMA_OVF	RW1C	0x0	If set, indicates vdma overflow.
		[0]	VDMA_UNF	RW1C	0x0	If set, indicates vdma underflow.
0x19	0x64	TPM_STATUS				HDMI Interface Control & Status
		[1]	HDMI_TPM_OOS	RW1C	0x0	If set, indicates TPM OOS at the HDMI interface.
		[0]	VDMA_TPM_OOS	RW1C	0x0	If set, indicates TPM OOS at the VDMA interface.
0x1a	0x68	CLIPP_MAX				HDMI Interface Control & Status
		[23:16]	R_MAXorCR_MAX	RW	0xf0	Defines the maximum value for clipping the red or red-difference chroma component. Default value are 0xf0 for red-difference chroma and 0xfe for red.
		[16:8]	G_MAXorY_MAX	RW	0x0eb	Defines the maximum value for clipping the green or luma component. Default values are 0xeb for luma and and 0xfe for green.
		[7:0]	B_MAXorCB_MAX	RW	0xf0	Defines the maximum value for clipping the blue or blue-difference chroma component. Default value are 0xf0 for blue-difference chroma and 0xfe for blue.
0x1b	0x6c	CLIPP_MIN				HDMI Interface Control & Status
		[23:16]	R_MINorCR_MIN	RW	0x10	Defines the minimum value for clipping the red or red-difference chroma component. Default value are 0x10 for red-difference chroma and 0x01 for red.
		[16:8]	G_MINorY_MIN	RW	0x010	Defines the minimum value for clipping the green or luma component. Default values are 0x10 for luma and and 0x01 for green.
		[7:0]	B_MINorCB_MIN	RW	0x10	Defines the minimum value for clipping the blue or blue-difference chroma component. Default value are 0x10 for blue-difference chroma and 0x01 for blue.
0x100	0x400	HSYNC_1				HDMI Interface Control & Status
		[31:16]	H_LINE_ACTIVE	RW	0x0000	This is the horizontal line active pixel width (active resolution length). e.g. 1920 (1080p)
		[15:0]	H_LINE_WIDTH	RW	0x0000	This is the horizontal line width (no. of pixel clocks per line). e.g. 2200 (1080p)
0x101	0x404	HSYNC_2				HDMI Interface Control & Status
		[15:0]	H_SYNC_WIDTH	RW	0x0000	This is the horizontal sync width (no. of pixel clocks). e.g. 44 (1080p)
0x102	0x408	HSYNC_3				HDMI Interface Control & Status
		[31:16]	H_ENABLE_MAX	RW	0x0000	This is the horizontal data enable maximum. It is the sum of H_ENABLE_MIN and the active pixel width. e.g. 2112 (192 + 1920) (1080p)
		[15:0]	H_ENABLE_MIN	RW	0x0000	This is the horizontal data enable minimum. It is the sum of horizontal back porch (number of clock cycles between the falling edge of HSYNC to the rising edge of DE) and the sync width. e.g. 192 (44 + 148) (1080p)
0x110	0x440	VSYNC_1				HDMI Interface Control & Status
		[31:16]	V_FRAME_ACTIVE	RW	0x0000	This is the vertical frame active line width (active resolution height). e.g. 1080 (1080p)
		[15:0]	V_FRAME_WIDTH	RW	0x0000	This is the vertical frame width (no. of lines per frame). e.g. 1125 (1080p)
0x111	0x444	VSYNC_2				HDMI Interface Control & Status
		[15:0]	V_SYNC_WIDTH	RW	0x0000	This is the vertical sync width (no. of lines). e.g. 5 (1080p)
0x112	0x448	VSYNC_3				HDMI Interface Control & Status
		[31:16]	V_ENABLE_MAX	RW	0x0000	This is the vertical data enable maximum. It is the sum of V_ENABLE_MIN and the active pixel height. e.g. 1121 (41 + 1080) (1080p)
		[15:0]	V_ENABLE_MIN	RW	0x0000	This is the vertical data enable minimum. It is the sum of vertical back porch (number of lines between the falling edge of VSYNC to the rising edge of DE) and the sync width. e.g. 41 (36 + 5) (1080p)

Access Type	Name	Description
RW	Read-write	Reads will return the current register value. Writes will change the current register value.
RO	Read-only	Reads will return the current register value. Writes have no effect.
RW1C	Read,write-1-to-clear	Reads will return the current register value. Writing the register will clear those bits of the register which were set to 1 in the value written. Bits are set by hardware.

Design considerations

Additional IPs needed:

• AXI DMAC

• AXI CLK Generator

• library/axi_spdif_tx

AXI DMAC provides a high-bandwidth direct memory access for the video stream. The core is configured as follows:

ad_ip_instance axi_dmac axi_hdmi_dma
ad_ip_parameter axi_hdmi_dma CONFIG.DMA_TYPE_SRC 0
ad_ip_parameter axi_hdmi_dma CONFIG.DMA_TYPE_DEST 1
ad_ip_parameter axi_hdmi_dma CONFIG.CYCLIC true
ad_ip_parameter axi_hdmi_dma CONFIG.DMA_2D_TRANSFER true
ad_ip_parameter axi_hdmi_dma CONFIG.DMA_DATA_WIDTH_DEST 64

The audio path is separated from the video path, for audio axi_spdif_tx core (axi_spdif_tx) is needed to transmit the audio information to the ADV7511 device. The whole system needs to be controlled by a processor (ARM or a soft core) that can programs the registers. axi_clkgen generates the clock frequency required for the desired resolution (pixel clock), the frequency is software configurable (Example adv7511_zc706 no-Os software).

Examples for different data width configurations

The ADV7511 can accept video data from as few as eight pins (either YCbCr 4:2:2 double data rate [DDR] or YCbCr 4:2:2 with 2x pixel clock) to as many as 36 pins (RGB 4:4:4 or YCbCr 4:4:4). In addition it can accept HSYNC, VSYNC and DE (Data Enable)

The axi_hdmi_tx core support the following video input connections:

• 36 bits with HSYNC, VSYNC and DE (projects/adv7511/vc707 development board)

• 24 bits with HSYNC, VSYNC and DE (projects/adv7511/zc706 development board)

• 16 bits with HSYNC, VSYNC and DE (projects/adv7511/zed)

• 16 bits with embedded SYNC (TX interface of the IMAGEON board)

Software support

The core can be controlled by no-Os or Linux

• Linux Driver

• Reference design with no-OS example

• projects/adv7511

References

• HDL IP core at library/axi_hdmi_tx

• AXI HDMI TX on wiki

• Zynq & Altera SoC Quick Start Guide

• FMC-IMAGEON Xilinx Reference Design

• ADV7511 Xilinx Evaluation Boards Reference Design