Motorola A008 Service Manual page 60

A008 / A6188+ – Circuit Description
The touch screen is controlled in the following way See Fig 1.
Touch screen control lines
- Right, Top, Left, Bottom
EL control lines
- EL (GND), EL (+)
- D0, D1, D2, D3
Control lines
- Disp, Loadse, Loadco, Dfseg, Dfcom,
Power lines
VD1, VD2, VM, VS12, Vdd, Vcc, Vss
Fig.1 LCD module electrical block diagram
Each row and column, is in effect a long imaginary resistor with a +ve voltage at one end
and a –ve or Grounded voltage level at the other. We can imagine that if these resistors
could be overlapped then we can create a comprehensive resistor matrix. It is this matrix
that provides us with the information of where the pen is placed on the touch screen. See
Fig 2 (Example values only)
1) The row drivers / Control Lines
Dragon Ball LLP
LOAD_IN before splitting to produce the 2 signals going to
DFSEG is originated from
polarisation) to J9805
on J9805 Pin 13
LCDOFF* From
FRAME – Used to indicate start of new frame
CP is originated from
J9805 Pin 10, where the signal becomes
Motorola Internal Use
Data lines
Frame, CP
+5V
Resistor values =1K
LOADCO
Pin K8 (latches line of data
Dragon Ball
where the signal becomes
Dragon Ball Pin M2 (switches LCD On or Off – NOT USED)
Dragon Ball LCLK
Touch screen
1/4 VGA
resolution LCD
EL panel
Row driver IC Row driver IC
(120 outputs) (120 outputs)
+5V
Resultant Data
1V (X)
3V (Y)
and LOADCE are originated from
J9805 where the signal becomes
J9805
LACD PIN L7 (used to toggle the crystal
DF_IN changing again to
PIN M7 (synchronises display data) to
CP
18
Fig 2
Pins 11 and 12
DFSEG