Owner's manual

Table Of Contents
26-4 DS785UM1
Copyright 2007 Cirrus Logic
Keypad Interface
EP93xx User’s Guide
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26
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