MMM sets keyboard mode. Intel Architecture and Architecture. The Shift input line status is stored along with every key code in FIFO in the scanned keyboard mode. Interface of Code given in text for reading keyboard. Conditional Statement in Assembly Language Program. Intrfacing input of is driven from the clock out of It then sends their relative response of the pressed key to the CPU and vice-a-versa.
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Microprocessor Microcontroller In a matrix keyboard there are keys which are arranged in the form of a matrix which consists of several rows and columns. In the figure which is stated below significantly indicates the interfacing process of a matrix keyboard which consists four rows and four columns respectively.
We connect a key at the intersection of every rows and columns. The lines of the columns get connected to Gnd through pull-down resistors. Presently, according to the given Byte pattern, logic 1 is sent out only on row 0. But no key is pressed on this row. As such, the input port receives the value from the keyboard because of the pull-down resistors as shown in the circuit diagram.
The reader might think about the key 9 that is pressed on row 2. But logic 0 is sent out presently on row 2. Hence only logic 0 is received on column 1 via the pressed key. The processor compares the value that is read from the input port with If both are same, it means that no key is pressed on row 0.
And in this way, all rows will get scanned one after another till the last row to detect the actual key pressed. Thus the keyboard will get interfaced by the microprocessor.
Interfacing a matrix keyboard with 8085 Microprocessor
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