Keyboard - Display Interface Circuit

4X4 matrix keyboard system settings, including 0 ~ 9 numeric keys. A ~ F as function keys. The main function of the keyboard is complete parameter settings, display mode select
Keyboard - Display Interface Circuit - schematic

ion, start automatic/manual arrangements, as well as the system and stop. Keyboard and display interface chip 8255A programmable circuit and connected to the microcontroller circuit shown in Figure 27-48. from this picture, you can see. 8255A to the B port as the display interface. The system uses a static display, 74LS373 as a latch. 74LS48 for the common cathode decoder/driver, LED digital tube with CS5137T. 44 keyboard matrix keyboard. 8255A port PA3-PAO row scan connection port column values from port B PB3 ~ PBO read people, to deal with the system keyboard interrupt. Thus, 8255A port B to work in two ways under: In the display state is output; the keyboard interrupt service routine processing input mode. To do this, just in front of the corresponding operation re 8255A new settings work.

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