From ead28dd6fed440ccf4667c459778012bb0d95733 Mon Sep 17 00:00:00 2001 From: "github-classroom[bot]" <66690702+github-classroom[bot]@users.noreply.github.com> Date: Thu, 5 Feb 2026 19:36:36 +0000 Subject: Initial commit --- vga-core/vga_adapter.v | 263 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 263 insertions(+) create mode 100644 vga-core/vga_adapter.v (limited to 'vga-core/vga_adapter.v') diff --git a/vga-core/vga_adapter.v b/vga-core/vga_adapter.v new file mode 100644 index 0000000..83e7413 --- /dev/null +++ b/vga-core/vga_adapter.v @@ -0,0 +1,263 @@ +/* VGA Adapter + * ---------------- + * + * This is an implementation of a VGA Adapter. The adapter uses VGA mode signalling to initiate + * a 640x480 resolution mode on a computer monitor, with a refresh rate of approximately 60Hz. + * It is designed for easy use in an early digital logic design course to facilitate student + * projects on the Altera DE2 Educational board. + * + * This implementation of the VGA adapter can display images of varying colour depth at a resolution of + * 320x240 or 160x120 superpixels. The concept of superpixels is introduced to reduce the amount of on-chip + * memory used by the adapter. The following table shows the number of bits of on-chip memory used by + * the adapter in various resolutions and colour depths. + * + * ------------------------------------------------------------------------------------------------------------------------------- + * Resolution | Mono | 8 colours | 64 colours | 512 colours | 4096 colours | 32768 colours | 262144 colours | 2097152 colours | + * ------------------------------------------------------------------------------------------------------------------------------- + * 160x120 | 19200 | 57600 | 115200 | 172800 | 230400 | 288000 | 345600 | 403200 | + * 320x240 | 78600 | 230400 | ############## Does not fit ############################################################## | + * ------------------------------------------------------------------------------------------------------------------------------- + * + * By default the adapter works at the resolution of 320x240 with 8 colours. To set the adapter in any of + * the other modes, the adapter must be instantiated with specific parameters. These parameters are: + * - RESOLUTION - a string that should be either "320x240" or "160x120". + * - MONOCHROME - a string that should be "TRUE" if you only want black and white colours, and "FALSE" + * otherwise. + * - BITS_PER_COLOUR_CHANNEL - an integer specifying how many bits are available to describe each colour + * (R,G,B). A default value of 1 indicates that 1 bit will be used for red + * channel, 1 for green channel and 1 for blue channel. This allows 8 colours + * to be used. + * + * In addition to the above parameters, a BACKGROUND_IMAGE parameter can be specified. The parameter + * refers to a memory initilization file (MIF) which contains the initial contents of video memory. + * By specifying the initial contents of the memory we can force the adapter to initially display an + * image of our choice. Please note that the image described by the BACKGROUND_IMAGE file will only + * be valid right after your program the DE2 board. If your circuit draws a single pixel on the screen, + * the video memory will be altered and screen contents will be changed. In order to restore the background + * image your circuti will have to redraw the background image pixel by pixel, or you will have to + * reprogram the DE2 board, thus allowing the video memory to be rewritten. + * + * To use the module connect the vga_adapter to your circuit. Your circuit should produce a value for + * inputs X, Y and plot. When plot is high, at the next positive edge of the input clock the vga_adapter + * will change the contents of the video memory for the pixel at location (X,Y). At the next redraw + * cycle the VGA controller will update the contants of the screen by reading the video memory and copying + * it over to the screen. Since the monitor screen has no memory, the VGA controller has to copy the + * contents of the video memory to the screen once every 60th of a second to keep the image stable. Thus, + * the video memory should not be used for other purposes as it may interfere with the operation of the + * VGA Adapter. + * + * As a final note, ensure that the following conditions are met when using this module: + * 1. You are implementing the the VGA Adapter on the Altera DE2 board. Using another board may change + * the amount of memory you can use, the clock generation mechanism, as well as pin assignments required + * to properly drive the VGA digital-to-analog converter. + * 2. Outputs VGA_* should exist in your top level design. They should be assigned pin locations on the + * Altera DE2 board as specified by the DE2_pin_assignments.csv file. + * 3. The input clock must have a frequency of 50 MHz with a 50% duty cycle. On the Altera DE2 board + * PIN_N2 is the source for the 50MHz clock. + * + * During compilation with Quartus II you may receive the following warnings: + * - Warning: Variable or input pin "clocken1" is defined but never used + * - Warning: Pin "VGA_SYNC" stuck at VCC + * - Warning: Found xx output pins without output pin load capacitance assignment + * These warnings can be ignored. The first warning is generated, because the software generated + * memory module contains an input called "clocken1" and it does not drive logic. The second warning + * indicates that the VGA_SYNC signal is always high. This is intentional. The final warning is + * generated for the purposes of power analysis. It will persist unless the output pins are assigned + * output capacitance. Leaving the capacitance values at 0 pf did not affect the operation of the module. + * + * If you see any other warnings relating to the vga_adapter, be sure to examine them carefully. They may + * cause your circuit to malfunction. + * + * NOTES/REVISIONS: + * July 10, 2007 - Modified the original version of the VGA Adapter written by Sam Vafaee in 2006. The module + * now supports 2 different resolutions as well as uses half the memory compared to prior + * implementation. Also, all settings for the module can be specified from the point + * of instantiation, rather than by modifying the source code. (Tomasz S. Czajkowski) + */ + +module vga_adapter( + resetn, + clock, + colour, + x, y, plot, + /* Signals for the DAC to drive the monitor. */ + VGA_R, + VGA_G, + VGA_B, + VGA_HS, + VGA_VS, + VGA_BLANK, + VGA_SYNC, + VGA_CLK); + + parameter BITS_PER_COLOUR_CHANNEL = 1; + /* The number of bits per colour channel used to represent the colour of each pixel. A value + * of 1 means that Red, Green and Blue colour channels will use 1 bit each to represent the intensity + * of the respective colour channel. For BITS_PER_COLOUR_CHANNEL=1, the adapter can display 8 colours. + * In general, the adapter is able to use 2^(3*BITS_PER_COLOUR_CHANNEL ) colours. The number of colours is + * limited by the screen resolution and the amount of on-chip memory available on the target device. + */ + + parameter MONOCHROME = "FALSE"; + /* Set this parameter to "TRUE" if you only wish to use black and white colours. Doing so will reduce + * the amount of memory you will use by a factor of 3. */ + + parameter RESOLUTION = "320x240"; + /* Set this parameter to "160x120" or "320x240". It will cause the VGA adapter to draw each dot on + * the screen by using a block of 4x4 pixels ("160x120" resolution) or 2x2 pixels ("320x240" resolution). + * It effectively reduces the screen resolution to an integer fraction of 640x480. It was necessary + * to reduce the resolution for the Video Memory to fit within the on-chip memory limits. + */ + + parameter BACKGROUND_IMAGE = "background.mif"; + /* The initial screen displayed when the circuit is first programmed onto the DE2 board can be + * defined useing an MIF file. The file contains the initial colour for each pixel on the screen + * and is placed in the Video Memory (VideoMemory module) upon programming. Note that resetting the + * VGA Adapter will not cause the Video Memory to revert to the specified image. */ + + parameter USING_DE1 = "FALSE"; + /* If set to "TRUE" it adjust the offset of the drawing mechanism to account for the differences + * between the DE2 and DE1 VGA digital to analogue converters. Set to "TRUE" if and only if + * you are running your circuit on a DE1 board. */ + + /*****************************************************************************/ + /* Declare inputs and outputs. */ + /*****************************************************************************/ + input resetn; + input clock; + + /* The colour input can be either 1 bit or 3*BITS_PER_COLOUR_CHANNEL bits wide, depending on + * the setting of the MONOCHROME parameter. + */ + input [((MONOCHROME == "TRUE") ? (0) : (BITS_PER_COLOUR_CHANNEL*3-1)):0] colour; + + /* Specify the number of bits required to represent an (X,Y) coordinate on the screen for + * a given resolution. + */ + input [((RESOLUTION == "320x240") ? (8) : (7)):0] x; + input [((RESOLUTION == "320x240") ? (7) : (6)):0] y; + + /* When plot is high then at the next positive edge of the clock the pixel at (x,y) will change to + * a new colour, defined by the value of the colour input. + */ + input plot; + + /* These outputs drive the VGA display. The VGA_CLK is also used to clock the FSM responsible for + * controlling the data transferred to the DAC driving the monitor. */ + output [9:0] VGA_R; + output [9:0] VGA_G; + output [9:0] VGA_B; + output VGA_HS; + output VGA_VS; + output VGA_BLANK; + output VGA_SYNC; + output VGA_CLK; + + /*****************************************************************************/ + /* Declare local signals here. */ + /*****************************************************************************/ + + wire valid_160x120; + wire valid_320x240; + /* Set to 1 if the specified coordinates are in a valid range for a given resolution.*/ + + wire writeEn; + /* This is a local signal that allows the Video Memory contents to be changed. + * It depends on the screen resolution, the values of X and Y inputs, as well as + * the state of the plot signal. + */ + + wire [((MONOCHROME == "TRUE") ? (0) : (BITS_PER_COLOUR_CHANNEL*3-1)):0] to_ctrl_colour; + /* Pixel colour read by the VGA controller */ + + wire [((RESOLUTION == "320x240") ? (16) : (14)):0] user_to_video_memory_addr; + /* This bus specifies the address in memory the user must write + * data to in order for the pixel intended to appear at location (X,Y) to be displayed + * at the correct location on the screen. + */ + + wire [((RESOLUTION == "320x240") ? (16) : (14)):0] controller_to_video_memory_addr; + /* This bus specifies the address in memory the vga controller must read data from + * in order to determine the colour of a pixel located at coordinate (X,Y) of the screen. + */ + + wire clock_25; + /* 25MHz clock generated by dividing the input clock frequency by 2. */ + + wire vcc, gnd; + + /*****************************************************************************/ + /* Instances of modules for the VGA adapter. */ + /*****************************************************************************/ + assign vcc = 1'b1; + assign gnd = 1'b0; + + vga_address_translator user_input_translator( + .x(x), .y(y), .mem_address(user_to_video_memory_addr) ); + defparam user_input_translator.RESOLUTION = RESOLUTION; + /* Convert user coordinates into a memory address. */ + + assign valid_160x120 = (({1'b0, x} >= 0) & ({1'b0, x} < 160) & ({1'b0, y} >= 0) & ({1'b0, y} < 120)) & (RESOLUTION == "160x120"); + assign valid_320x240 = (({1'b0, x} >= 0) & ({1'b0, x} < 320) & ({1'b0, y} >= 0) & ({1'b0, y} < 240)) & (RESOLUTION == "320x240"); + assign writeEn = (plot) & (valid_160x120 | valid_320x240); + /* Allow the user to plot a pixel if and only if the (X,Y) coordinates supplied are in a valid range. */ + + /* Create video memory. */ + altsyncram VideoMemory ( + .wren_a (writeEn), + .wren_b (gnd), + .clock0 (clock), // write clock + .clock1 (clock_25), // read clock + .clocken0 (vcc), // write enable clock + .clocken1 (vcc), // read enable clock + .address_a (user_to_video_memory_addr), + .address_b (controller_to_video_memory_addr), + .data_a (colour), // data in + .q_b (to_ctrl_colour) // data out + ); + defparam + VideoMemory.WIDTH_A = ((MONOCHROME == "FALSE") ? (BITS_PER_COLOUR_CHANNEL*3) : 1), + VideoMemory.WIDTH_B = ((MONOCHROME == "FALSE") ? (BITS_PER_COLOUR_CHANNEL*3) : 1), + VideoMemory.INTENDED_DEVICE_FAMILY = "Cyclone II", + VideoMemory.OPERATION_MODE = "DUAL_PORT", + VideoMemory.WIDTHAD_A = ((RESOLUTION == "320x240") ? (17) : (15)), + VideoMemory.NUMWORDS_A = ((RESOLUTION == "320x240") ? (76800) : (19200)), + VideoMemory.WIDTHAD_B = ((RESOLUTION == "320x240") ? (17) : (15)), + VideoMemory.NUMWORDS_B = ((RESOLUTION == "320x240") ? (76800) : (19200)), + VideoMemory.OUTDATA_REG_B = "CLOCK1", + VideoMemory.ADDRESS_REG_B = "CLOCK1", + VideoMemory.CLOCK_ENABLE_INPUT_A = "BYPASS", + VideoMemory.CLOCK_ENABLE_INPUT_B = "BYPASS", + VideoMemory.CLOCK_ENABLE_OUTPUT_B = "BYPASS", + VideoMemory.POWER_UP_UNINITIALIZED = "FALSE", + VideoMemory.INIT_FILE = BACKGROUND_IMAGE; + + vga_pll mypll(clock, clock_25); + /* This module generates a clock with half the frequency of the input clock. + * For the VGA adapter to operate correctly the clock signal 'clock' must be + * a 50MHz clock. The derived clock, which will then operate at 25MHz, is + * required to set the monitor into the 640x480@60Hz display mode (also known as + * the VGA mode). + */ + + vga_controller controller( + .vga_clock(clock_25), + .resetn(resetn), + .pixel_colour(to_ctrl_colour), + .memory_address(controller_to_video_memory_addr), + .VGA_R(VGA_R), + .VGA_G(VGA_G), + .VGA_B(VGA_B), + .VGA_HS(VGA_HS), + .VGA_VS(VGA_VS), + .VGA_BLANK(VGA_BLANK), + .VGA_SYNC(VGA_SYNC), + .VGA_CLK(VGA_CLK) + ); + defparam controller.BITS_PER_COLOUR_CHANNEL = BITS_PER_COLOUR_CHANNEL ; + defparam controller.MONOCHROME = MONOCHROME; + defparam controller.RESOLUTION = RESOLUTION; + defparam controller.USING_DE1 = USING_DE1; + +endmodule + \ No newline at end of file -- cgit v1.2.3