User Guide

NHM-8NX
System Module & UI PAMS Technical Documentation
Page 40 ãNokia Corporation Issue 1 05/02
The power part consists of a current limited switch, and is controlled by a logic enable
(on/off) via KLIGHT. On/off is synchronised with "VIBRA" signal SW wise, but can have
independent SW control.
Keyboard
The keyboard used in NHM-8NX is partly matrix ("metal dome" type) and partly individu-
ally interrupts, this is needed for supporting multiplekeypresses.
The keyboard PWB layout consists of a grounded outer ring and either a "cake pattern"
grid (matrix) or an inner pad. This construction makes the keys immune for ESD, as the
keydome will have a low ohmic contact with the PCB ground
Figure 14: Keyboard layout
All lines are configured as input, when there is no key pressed, the inputs are high due to
that the UPP has internally pull-up resistors on those lines. When a key is pressed, the
specific lines where the key is placed is pulled low. This generates an interrupt to the
MCU and the MCU now starts its scanning procedure.