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EN6370B Datasheet(PDF) 22 Page - Sanyo Semicon Device |
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EN6370B Datasheet(HTML) 22 Page - Sanyo Semicon Device |
22 / 38 page LC75808W No.6370-22/38 Key Scan Operation Functions 1. Key scan timing The key scan period is 384T(s). To reliably determine the on/off state of the keys, the LC75808W scans the keys twice and determines that a key has been pressed when the key data agrees. It outputs a key data read request (a low level on DO) 800T(s) after starting a key scan. If the key data dose not agree and a key was pressed at that point, it scans the keys again. Thus the LC75808W cannot detect a key press shorter than 800T(s). Note: *3. Note that the high/low states of these pins are determined by the KC1 to KC6 bits in the control data, and that key scan output signals are not output from pins that are set to low. 2. In normal mode • The pins KS1 to KS6 are set to high or low by the KC1 to KC6 bits in the control data. • If a key on one of the lines corresponding to a KS1 to KS6 pin which is set high is pressed, a key scan is started and the keys are scanned until all keys are released. Multiple key presses are recognized by determining whether multiple key data bits are set. • If a key is pressed for longer than 800T(s) (Where T= ) the LC75808W outputs a key data read request (a low level on DO) to the controller. The controller acknowledges this request and reads the key data. However, if CE is high during a serial data transfer, DO will be set high. • After the controller reads the key data, the key data read request is cleared (DO is set high) and the LC75808W performs another key scan. Also note that DO, being an open-drain output, requires a pull-up resistor (between 1k Ω and 10k Ω). 1 fOSC 800T [s ] 800T [s] 800T [s ] Serial data transfer Serial data transfer Serial data transfer Key address(43H) Key address Key address Key data read request Key data read Key data read Key data read request Key data read Key data read request A12912 Key input 1 Key input 2 Key scan CE DI DO fosc 1 T= 1 *3 *3 KS1 2 *3 *3 KS2 3* 3 *3 KS3 4* 3 *3 KS4 5 1 2 3 4 5* 3 *3 KS5 6 768T [s] 6 A12911 *3 *3 KS6 Key on fosc 1 T= |
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