Selects the number of display positions, type of key scan Programs internal clk, sets scan and debounce times. Selects type of FIFO read and address of the read. Selects type of display read and address of the read.
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You can change your ad preferences anytime. Upcoming SlideShare. Like this presentation? Why not share! Embed Size px. Start on. Show related SlideShares at end. WordPress Shortcode. Aisu Follow. Published in: Technology. Full Name Comment goes here. Are you sure you want to Yes No.
DrLucyThomas Nice!! Show More. Padhu Nathan. Alefthaha Alefthaha. No Downloads. Views Total views. Actions Shares. Embeds 0 No embeds. No notes for slide. WHY ??? If during a single debounce period two keyboard scans two keys are found pressed , this is considered a simultaneous depression and an error flag is set. In the sensor matrix mode, the debounce logic is inhibited.
The status of the sensor switch matrix is fed directly to sensor RAM matrix. Thus the sensor RAM bits contains the rowwise and column wise status of the sensors in the sensor matrix.
AI is a bit in read sensor RAM word. PPPPP is a 5-bit binary constant. The input frequency is divided by a decimal constant ranging from 2 to 31, decided by the bits of an internal prescaler, PPPPP. The will automatically drive data bus for each subsequent read, in the same sequence, in which the data was entered. The same address counter is used for reading and writing.
Once a nibble is masked by setting the corresponding IW bit to 1, the entry to display RAM does not affect the nibble even though it may change the unmasked nibble. The blank display bit flags BL are used for blanking A and B nibbles. If the user wants to clear the display, blank BL bits are available for each nibble as shown in format.
Both BL bits will have to be cleared for blanking both the nibbles. You just clipped your first slide! Clipping is a handy way to collect important slides you want to go back to later. Now customize the name of a clipboard to store your clips.
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8279 - Programmable Keyboard
The keyboard first scans the keyboard and identifies if any key has been pressed. It then sends their relative response of the pressed key to the CPU and vice-a-versa. The Keyboard can be interfaced either in the interrupt or the polled mode. In the Interrupt mode , the processor is requested service only if any key is pressed, otherwise the CPU will continue with its main task. In the Polled mode , the CPU periodically reads an internal flag of to check whether any key is pressed or not with key pressure. The keyboard consists of maximum 64 keys, which are interfaced with the CPU by using the key-codes.
8279 Programmable Keyboard - Microprocessor