Abstract: This paper introduces a practical and efficient LED large screen display control circuit, which features fast refresh rate, high brightness, and low power consumption. Keywords : LED large screen scanning 0 Overview LED large screen display systems have the characteristics of intuitive picture, flexible and varied content, and low cost, so they are widely used in public places for displaying text and simple image information. Due to the large number of pixels in LED large screens, dynamic scanning is often used to save hardware. Taking line-by-line scanning as an example, the display process is generally as follows: (1) Send a line of content in the display buffer to the display latch; (2) Light up the line and delay; (3) Blank the line, and then move the pointer down one line and repeat the above process. This method is feasible for small LED display systems, but for large screens, as the number of pixels increases, data transmission will take a lot of time, and the display brightness of the screen will decrease significantly. Especially for outdoor large screen display systems, this method will not achieve practical results. This paper introduces a novel display control circuit that can effectively solve this problem. 1 Composition and working principle of the control circuit The LED large screen display circuit is shown in Figure 1. The entire circuit consists of two parts: the main control circuit and the display circuit. The main control part is composed of a DS80C320MPU, a 27C040EPROM, an AT29C040, a FLASHMEMORY, a 62256SRA M, and peripheral circuits. The DS80C320 is a high-speed microprocessor manufactured by Dallas Semiconductor. It is instruction-compatible with the 8051 but is more than 6 times faster, and includes power monitoring circuitry and a watchdog timer. Its unique dual data pointers are used to quickly store LED dot matrix data into the display buffer, implemented as follows: EQUDSP, #86H; pointer selection bit MOVR5, #0FFH; number of bytes to transfer MOVDPTR, #DHDL; load destination address INCDSP; change pointer MOVDPTR, #SHSL; load source address MOVE:; loop. If a 25MHz crystal oscillator is selected, executing the above program takes 702μs, which is half the time compared to the 8051. After system startup, the DS80C320 writes relevant control words to the MC6845 and stores the image information displayed on the LED screen in the display buffer. The MC6845 and AT89C2051 control the display. Simultaneously, the DS80C320 receives display information via the RS-485 communication port and converts it into LED dot matrix data, storing it in the FLASHMEMORY for future LED screen updates. The display section consists of a display buffer 62256, a CRT controller MC6845, a microprocessor AT89C2051, a multiplexer 74HC157, a row and column latch CD4094, and other circuitry. The AT89C2051 is a 20-pin high-performance CMOS 8-bit microprocessor manufactured by Atmel, compatible with the MCS-51 instruction set. The MC6845 primarily functions as the display address scanner. Its internal character height register R9 is set to 2, indicating 3 character scan lines. Other control words are selected appropriately according to the LED screen specifications. The square wave generated by the AT89C2051 serves as the CLK signal for the MC6845, while the RA0 value of the MC6845 acts as the enable signal for the display memory by the DS80C320. If the LED screen is 256 rows × 1024 columns, taking row scanning as an example, the display process is as follows: The AT89C2051 pre-writes 10000…0 (255 zeros) into the row latch, and then, under the control of its internal timer and counter, issues 128 CLK signals. After each signal is issued, the display memory address output by the MC6845 is incremented by 1. The AT89C2051 reads parallel 8-bit data from the display memory's data port and converts it into serial data, storing it in the column latch CD4094. During this period, RA0 remains low, and the DS80C320 does not operate on the display memory. After sending 128 CLK signals, the AT89C2051 immediately clears the screen (P3.3 = 0) and sends a pulse through pin P3.2 to move the row pointer down. Then, P3.7 = 1 latches all the data in the column latches into the output, lighting up the corresponding row (P3.3 = 1). After a delay, the AT89C2051 sends another 128 CLK signals, this time RA0 = 1. The DS80C320 can then operate on the display memory. This process is repeated to achieve dynamic display on the LED screen. The DS80C210 can synchronously add a row of content into the display buffer with the row pointer, ensuring high-quality animation. Thanks to the use of the MC6845, scrolling functionality is easily implemented.