Samsung S3C6400X User Manual page 1142

KEYPAD INTERFACE
KEY PAD SCANNING PROCEDURE
At initial state, all column lines (outputs) are low level. When column data output tri-state enable bits are all high,
and the tri-state enable mode is not used, these bits must be written to zeros. When no key pressed state, all
row lines (inputs) are high (used pull-up pads). When any key is pressed, the corresponding row and column
lines are shortened together and a low level is driven on the corresponding row line, generating a keypad
interrupt. The CPU (software) writes with a LOW level on one column line and HIGH on the others to the
KEYIFCOL register. In each write time, the CPU reads the value of the KEYIFROW register and detects if one
key of the corresponding column line is pressed. When the scanning procedure is end, the pressed key (one or
more) can be detected.
Preliminary product information describe products that are in development,
40-4
for which full characterization data and associated errata are not yet available.
Specifications and information herein are subject to change without notice.
Figure 40-3 Keypad scanning procedure I
S3C6400X III RISC MICROPROCESSOR