89C52 single-chip parallel I / O port to achieve a number of LED display
Applications in single-chip system, the widespread use of low-cost and flexible digital control (LED) displays do. Commonly used for 4 to eight 8-bit digital tube LED display, that is, 4 ~ 8 LED digital tube. This shows that the method to achieve a lot, but appropriate measures must be used to achieve a number of LED display. This paper presents a design methodology, designed to use the multi-channel digital tube LED display system with a hardware device is simple, better portability, low cost, in a variety of instrumentation display system in the application of results.
1 hardware circuit
A number of LED displays, often above all bit lines in parallel with the election, by an 8-bit I / O port control, and common cathode or anode point total from the other eight I / O port control; also can be constitute a parallel expansion of the mouth show circuit, generally, need to expand the more pin devices, the higher the price. This article will introduce a single chip using a parallel I / O port to achieve more than a simple LED display method shown in Figure 1 is the circuit schematic diagram of the hardware. Which, 74LS138 is a 3-wire line -8 decoder, 74LS164 8-bit parallel output serial input gated shift register, LED cathode using a total of L05F-based digital control.
Display, the display data from a serial port P12 of 89C52 output sent to the 74LS164 shift register A, B side, and then into the parallel data output from the Q0 ~ Q7 output to control the switch WT1 ~ WT8 the collector, and then the LED above the output selection code at the same time sent to the digital control LED1 ~ LED8. 89C52-bit selection code from the output port P14 ~ P16 and sent by the 74LS138 decoder switch Y1 ~ Y8 the base to the digital control bit LED1 ~ LED8 for election control, so that digital control will be 8 to 100ms of time interval shows a rotational basis. As a result of the residual effects of the human eye, this 8 digital tube display looks almost the same time.
2 software programming
Software programming of the system using MCS-51 series single-chip assembly language completed and the display program as a subroutine, so that the main program to call their convenience. As shown in Figure 2 is a flow chart. Specific procedure code is as follows:
The design method has been applied to single-chip experiment students display circuit and display system in a variety of instruments. As long as the show transferred to other procedures in the main program to complete the display. After repeated use of proof: The method is portable, and practical.
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