Datasheet

19
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TSC2000
SBAS257
FIGURE 8. X- and Y-Coordinate Touch Screen Scan, Initiated by Touch.
Screen
Touch
Issue Interrupt
PENIRQ
Go to Host-Controlled
Conversion
Touch Screen Scan
X and Y
PENIRQ Initiated
Done
Done
No
No
Yes
Yes
Yes
No
No
Yes
Is Data
Averaging Done
Is Screen
Touched
Is Panel Voltage
Stabilization Done
Turn On Drivers: Y+, Y–
Start Clock
Store Y-Coordinates in
Y-Register
Power Down A/D Converter
Power Up A/D Converter
Reset PENIRQ and
Scan Trigger
Turn Off Clock
Convert Y-Coordinates
Is PSM = 1
No
Yes
No
Is Screen
Touched
Is Data
Averaging Done
No
Yes
Yes
Is Panel Voltage
Stabilization Done
Convert X-Coordinates
Turn On Drivers: X+, X–
Power Up A/D Converter
Store X-Coordinates in
X-Register
Reset PENIRQ and
Scan Trigger
Power Down A/D Converter
Turn Off Clock
Issue Data Available
The time needed to get a complete X/Y-coordinate reading
can be calculated by:
(3)
t 2.5 s + 2 t + t + t 2N N
1
f
s
COORDINATE PVS
PRE
SNS AVG BITS
CONV
=
( )
+•+µ






µ 44.
where,
t
COORDINATE
= time to complete X/Y-coordinate reading
t
PVS
= Panel Voltage Stabilization time, see Table XII
t
PRE
= precharge time, see Table XXII
t
SNS
= sense time, see Table XXIII
N
AVG
= number of averages, see Table X; for no averag-
ing, N
AVG
= 1
N
BITS
= number of bits of resolution, see Table IX
f
CONV
= A/D converter clock frequency, see Table XI
If the pressure of the touch is also to be measured, the
process will continue in the same way, but measuring the Z
1
and Z
2
values, and placing them in the Z
1
and Z
2
registers,
see Figure 9. As before, this process time depends upon the
settings described above. The time for a complete X, Y, Z
1
,
and Z
2
coordinate reading is given by:
(4)
t 4.75 s + 3 t + t + t 4N N
1
f
s
COORDINATE PVS
PRE
SNS AVG BITS
CONV
=µ
( )
+•+µ






44.