Description of  Program

(Bus)

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Flowchart for Bus  Program

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Simple description of Bus  Program:

    When the program is started, the buffer register and flag will be initialized, and then the main loop waits for the interrupt.
ƒ° The main loop will start, if got the interrupt, it will scanned four column by the keypad, if there are 4 column scanned, it will check have any key is press, then find the key which is pressed and corresponding seven segment display from the database.
ƒ° If the program haven¡¦t scanned all four columns or cannot detect any key press, then it will go back to the main loop.
ƒ° After find the corresponding display, the program will update the display buffer and find which key cycle is. Refer to the table P1. If the key valid is in this cycle, it will set the valid flag of the cycle. If no, it will clear the valid flag of the cycle.
     Then it will check the four valid flag is set all or not. If no, it will return to the main loop to repeat the program. If yes, it will send the output signal form the display buffer with last bus switch (Refer to the table P2). Then will clear all the flag to return back to the main loop and repeat the program again.

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