MOTOROLA
KEYPAD PORT
MMC2001
14-8
REFERENCE MANUAL
Figure 14-6 Keypad Synchronizer Functional Diagram
14.4.6 Multiple Key Closures
One or two keys pressed simultaneously are easily detected by the software. When
three or more keys are pressed, however, it is possible that errant key closures may
be detected. As can be seen in Figure 14-7, three keys pressed simultaneously can
short between the column currently “scanned” by software and another column.
Depending on the location of the third key pressed, a “ghost” key press may be
detected.
Keypad
256 Hz
Matrix
. . .
FF
D Q
FF
D Q
FF
D Q
FF
D Q
^S
R
Clear KPKD Status Flag
NAND
R
R
R
R
KPKD
FF
D Q
FF
D Q
FF
D Q
FF
D Q
^S
R
S
S
S
S
KPKR
Clear KPKR Status Flag
Clear KPKD Synchronizer
Set KPKR Synchronizer
Freescale Semiconductor,
I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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