Lcd - Nokia NSB-9 Service Manual

CCS Technical Documentation
LCD and engine SW & control keys LEDs are driven in serial mode (3 + 3 connected par-
allel) by a LED driver to achieve stable and bright backlightning. 33R resistor is used to
define the proper current for LCD backlightning (about 16mA). The feedback signal Vfb
(voltage across 33R) is used to control the current. LED driver will increase or decrease
the output voltage for LEDs to keep the current stable. If current path through LCD LEDs
is open, current is at its maximum and it flows through the three other LEDs

LCD

NSB-9 has 130 x 130 8bpp (bits per pixel) passive matrix colour STN display. Interface is
using 9 bit data transfer. D/C bit is set during each transmitted byte.
UPP drives the CSX pin low and starts by setting the D/C-bit (data/command) to SDA. The
bit is read by the display on the first rising edge of CLK. On the next falling edge of CLK
the MSB data bit (D7) is set to SDA by the engine. On the next falling edge of CLK the
next bit (D6) is set to SDA. This continues until all 8 bits have been transmitted.
Issue 1 04/03
Figure 10: Engine qwerty keypad LED connection
Nokia Corporation
System Module and User Interface
NSB-9
Page 37