
26-4 DS785UM1
Copyright 2007 Cirrus Logic
Keypad Interface
EP93xx User’s Guide
• No press for address 0x1B at (ROW3, COL3)
The ignored addresses, 0x18 and 0x1B, are greater than the addresses of the two keys
detected. The following controller actions occur:
• ROW0 is driven low.
• When ROW0 is low, COL0 and COL3 are also low due to the current paths formed by
the keys pressed.
• During the time that ROW1 is low each of the columns (COL0 through COL7) is
scanned.
• Since COL0 is low the key 0x00 appears to be pressed.
Figure 26-3. Apparent Key 00H
ROW 0
KEY 00H KEY 01H
KEY 02H KEY 03H KEY 04H KEY 05H
KEY 06H KEY 07H
ROW 1
KEY 08H KEY 09H
KEY 0AH KEY 0BH KEY 0CH KEY 0DH
KEY 0EH KEY 1FH
ROW 2
KEY 10H KEY 11H
KEY 12H KEY 13H KEY 14H KEY 15H
KEY 16H KEY 17H
ROW 3
KEY 18H KEY 19H
KEY 1AH KEY 1BH KEY 1CH KEY 1DH
KEY 1EH KEY 1FH
ROW 4
KEY 20H KEY 21H
KEY 22H KEY 23H KEY 24H KEY 25H
KEY 26H KEY 27H
ROW 5
KEY 28H KEY 29H
KEY 2AH KEY 2BH KEY 2CH KEY 2DH
KEY 2EH KEY 2FH
ROW 6
KEY 30H KEY 31H
KEY 32H KEY 33H KEY 34H KEY 35H
KEY 36H KEY 37H
ROW 7
KEY 38H KEY 39H
KEY 3AH KEY 3BH KEY 3CH KEY 3DH
KEY 3EH KEY 3FH
COL 0 COL 1 COL 2 COL 3 COL 4 COL 5 COL 6 COL 7
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