Zilog Z8F0411 - Manual (Page 19)

MDS General-Purpose Board Development Kit
User Manual
UM016905-1207 MDS-GP Board Features
14
Keypad
Figure 7 displays the MDS-GP board with a 3 x 4 matrix keypad. The
keypad is controlled using GPIO port B. The four ROW pins have 10 K
pull-up resistors and are configured as inputs. The three COL pins are
configured as outputs. The software examples in this kit operate as
follows:
•
All ROW pins are configured as inputs, All COL pins are configured
as outputs and are initialized High.
•
In a interrupt routine, one COL pin is set Low and the ROW pins are
polled to check for a Low state.
•
If any ROW pin is polled Low, the key scan interrupt routine returns
the key pushed.
•
On each interrupt, a new COL pin is set Low. Three interrupts are
required to perform a full scan.
ZNEO ® Z16F processor module requires minor changes for
keypad interfacing. See ZNEO ® Z16F in Appendix—MDS-PM
Board Pin Maps on page 33.
Note: