AN980 Datasheet, PDF (6/8 Pages) STMicroelectronics – ST7 KEYPAD DECODING TECHNIQUES

ST7 KEYPAD DECODING TECHNIQUES, IMPLEMENTING WAKE-UP ON KEYSTROKE
5 FLOWCHARTS
Figure 2. Flowchart: Main program
Initializations
infinite
loop
HALT
Figure 3. Flowchart: external interrupt (EI1)
X = 48 (3x16 coded values)
one column activated
(PA0...PA3)
Is there a low level on the
intersection of the stored
row and column?
yes
no
store into X
next column
value
corresponding value of the pressed key
stored into A, X and sent on LEDS
EXIT
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