Nokia 5140 Service Manual

Nokia Customer Care

System Module and User Interface

NPL-4/5

Issue 1 05/04

Copyright © 2004 Nokia Corporation. All rights reserved.

Page 67

NPL-4/5 consists of separate UI board, type designate wk4, which includes contacts for 

the keypad domes, Functional cover interface pads, Thermoter thermistor and LED’s for 
keypad lighting. UI board is connected to main PWB through 20 pole board-to-board 
connector with springs. 

5x5-matrix keyboard is used in NPL-4/5. Key pressing is detected by scanning procedure. 
Keypad signals are connected UPP keyboard interface.

When no key is pressed, row inputs are high due to UPP internal pull-up resistors. The 
columns are written zero. When key is pressed one row is pulled down and an interrupt is 
generated to MCU. After receiving interrupt, MCU starts scanning procedure. All columns 
are first written high and then one column at the time is written down. All other col-
umns except one, which was written down, are set as inputs. Rows are read while col-
umn at the time is written down. If some row is down it indicates that key which is at 
the cross point of selected column and row was pressed. After detecting pressed key all 
register inside the UPP are reset and columns are written back to zero.

ROW0

VOL+

LEFT

SEND

END

RIGHT

ROW1

VOL-

SOFT LEFT

UP

DOWN

SOFT RIGHT

ROW2

1

4

7

*

ROW3

SELECT

2

5

8

0

ROW4

PTT

3

6

9

#

ROW 0
ROW 1
ROW 2
ROW 3
ROW 4

COL 0
COL 1
COL 2
COL 3
COL 4