In recent years, with the rapid development of computer technology and integrated circuit technology, widely used large-screen display system was undoubtedly the video LED display system. In the LED display technology, due to the red, green light-emitting diode brightness, light color performance and other performance has also been greatly improved, coupled with the development of computer multimedia production software, pseudo-color video LED display system manufacturing costs are greatly reduced, The field is increasing. This pseudo-color video LED display system uses a computer multimedia technology, full dynamic display of video images, clear images, high brightness, no patchwork, each color of the video gray level has been increased by the early 16 gray scale now 256 gray, with the development of large-scale integrated circuits and special components, 256 gray-scale full-color video LED display system at any time may be achieved.
LED electronic display technology has developed rapidly, has become one of the leading areas of today's flat panel display.
This article focuses on using M4A5-128P64-10VC design LED display control circuit.
1 LED display structure
In the LED display system, the lattice structure unit is the basic structure. Each display drive unit is a number of 8 × 8 dot matrix LED display module. Through a number of display drive board assembled together to form a number of square meters of the display, can be used to display a variety of text, images. LED display including computer video capture circuit, control circuit, drive circuit and power supply
LED display with red and green two primary colors, each color 256 gray, pixel pitch of 7.62mm, the pixels in the horizontal direction can reach 1024 points, the vertical direction can reach 768 points.
2 LED electronic display features
LED display is made by a number of display unit stitching, and its display using LED dot matrix and computer display screen mapping principle, that LED dot matrix pixel corresponds to a computer display of a pixel, such as computer Screen on the screen by resolution is divided into 640 columns, 480 lines, that is, LED display on the 640 × 480 dot matrix unit, each lattice unit and red, green and blue three light-emitting diodes, these three light-emitting diodes According to the principle of optical three primary colors, we only collect the image of each point on the computer screen to digitize and decompose into red, green and blue signals, through the system to deal with the three colors of light color, , Then passed to the LED dot matrix screen on the dot matrix unit, respectively, the corresponding color of the light-emitting diodes, that is, to achieve the computer screen on the LED dot matrix screen mapping.
3 LED electronic display drive principle
In most LED display systems, are used to refresh the drive method, that is, each LED display drive unit to the latch data, in the line to scan, according to LED display drive board structure, using 1P16 scan duty cycle.
We designed the LED display driver board drive circuit with two 74HC595 composed of 4:16 line decoder, which provides the entire scan circuit required line signal, but also with 74HC595 chip for serial shift register, it will system The resulting serial data shift becomes a parallel signal output, so that the drive column needs to provide a serial shift clock, a parallel lock signal and an output enable signal, line scan requiring serial data input and serial shift clock signal
M4A5-128P64-10VC is Lattice's CPLD devices, with 128 macro units and 64 IPO pins. Lattice development software ispDesignEXPERT integrates design input, compilation, validation and programming all work. First design input, you can directly draw the schematic, can also be used VHDL programming language.
Design file input after the compilation, and then the user can adjust the pin assignment, compile through, you can program the chip. Use the Byte-Blaster download cable to connect the computer parallel port to the JTAG socket on the PCB and program the installed chip after power-on.
Practice shows that the design of the M4A5-128P64-10VC circuit manufactured by Lattice has met the design requirements.