Nokia RH-6 Series Baseband Description & Troubleshooting page 29

CCS Technical Documentation
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 its scanning procedure. All col-
umns are first written high and then one column at the time is written down. All other
columns 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
ROW0
ROW1
ROW1
ROW2
ROW2
ROW3
ROW3
ROW4
ROW4
COL0
COL0
COL1 COL1
COL2
COL2
COL3 COL3
UPP interrupt
Issue 1 10/2003
Company Confidential
Figure 15. ROW1 and Col3 key pressed
© 2003 Nokia Corporation.
6 - BB Description & Troubleshooting
RH-6
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