Summary : This paper presents a practical and efficient large led display display control circuit, the circuit has a fast refresh rate, high brightness, low power consumption.
Large
Led display with a screen visual display system, content flexibility, low cost and so on, so it is widely used in public places in the text and simple display of image information. The large LED display pixels and more often used to save the dynamic scanning hardware. To progressive scan, for example, indicates that the process is generally: (1) to display the contents of the cache line into the display latch; (2) lights up the line and delay; (3) line blanking, and then the pointer down line and repeat the process. LED display shows for small systems, this approach is feasible, but large led display is increased as the pixel data transfer will take a lot of time, the screen display brightness will be significantly decreased, especially for outdoor The large led display display system, and then designed using this method can not achieve more practical results. This paper describes a novel display control circuit can effectively solve this problem.
1, the control circuit components and working principle
Large LED display shows the circuit shown in Figure 1.
The entire circuit from the main control circuit and display circuit composed of two parts.
Master part by DS80C320MPU, 27C040EPROM, AT29C040, FLASHMEMORY, 62256SRAM and peripheral circuit. DALLAS DS80C320 which is produced by the U.S. high-speed microprocessor, which is compatible with the 8051 directive, but more than 6 times faster, incorporates power monitoring circuitry, watchdog and so on. Its unique dual data pointers to the data quickly into the LED dot matrix display buffer, the realization of the following:
EQUDSP, # 86H; pointer select bits
MOVR5, # 0FFH; the number of bytes transferred
MOVDPTR, # DHDL; into the destination address
INCDSP; change the pointer
MOVDPTR, # SHSL; into the source address
MOVE:; cycle
If the election 25MHz crystal, this process requires the implementation of the above 702s, compared with 8051 can save half the time. After system startup, DS80C320 control word written to the relevant MC6845 and large LED display shows the screen display information into the cache, MC6845 and AT89C2051 control screen display, while DS80C320 through communication port 485 to receive display information, and convert into the LED dot matrix display data into FLASHMEMORY to prepare for large LED display in the frame.
Display in part by the display buffer 62256, CRT controller MC6845, microprocessor AT89C2051, multi-address translator 74HC157, CD4094 and the ranks of other parts of latch circuit. Atmel AT89C2051 is a company of which 20 feet high CMOS8 bit microprocessor, which is compatible with the MCS-51 instruction. MC6845 major role since the scan shows the address, height of the characters within it to take 2 registers the value of R9, the three characters in scan lines, and other control word according to the specifications of large screen LED appropriate selection, AT89C2051 square wave generated by the CLK signal as the MC6845 , while the MC6845's RA0 value of the display memory as the DS80C320 allows the signal, if the LED large screen of 256 (rows) 1024 (columns) to line scanning, for example, shown as follows: AT89C2051 advance 10000 ... 0 (255 zero) written to the row latch, then in control of the internal timer and counter issued under the CLK signal 128, each signal is issued, MC6845 output of the memory address plus 1, AT89C
2051 data from the memory read port 8-bit parallel data into serial data and converts it into the column latches CD4094, which has been low during the RA0, DS80C320 not memory operations. 128 CLK signal to send, AT89
C2051 immediately clear screen (P3.3 = 0), and send a pulse through the P3.2 pin, so that the pointer down the line, and then from P3.7 = 1 all the columns of data into the latch output, and light up the line (P3.3 = 1); and delay, AT89C2051 recurrence CLK signal 128, then RA0 = 1, DS80
C320 memory can operate at this time, the process is repeated to achieve a dynamic large screen LED display.
DS80C210 synchronously with the line pointer to the contents of said line into the display buffer, thus ensuring high-quality animation to achieve. As a result of MC6845, scroll feature in Large led display is easy to achieve.
