Datasheet

26
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TSC2000
SBAS257
FIGURE 15. X-Coordinate Reading Controlled by Host.
Screen
Touch
Issue Interrupt
PENIRQ
Go to Host-Controlled
Conversion
Host-Controlled
X-Coordinate
No
Start Clock
Reset PENIRQ
No
Is Panel Voltage
Stabilization Done
Turn On Drivers: X+, X–
Turn On Drivers: X+, X–
No
Yes
Yes
Yes
No
Is Data
Averaging Done
Convert X-Coordinates
Start Clock
Power Up A/D Converter
Is PSM = 1
Are Drivers On
Done
Done
Host Writes A/D
Converter
Control Register
Host Writes A/D
Converter-
Control Register
Done
Power Down A/D Converter
Turn Off Clock
Issue Data Available
Store X-Coordinates
in X-Register
Conversion Controlled by the Host
In this mode, the TSC2000 will detect when the touch panel
is touched and cause the
PENIRQ line to go LOW. The host
will recognize the interrupt request. Instead of starting a
sequence in the TSC2000 which then reads each coordinate
in turn, the host now must control all aspects of the conver-
sion. Generally, upon receiving the interrupt request, the host
will turn on the Y-drivers. After waiting for the settling time,
the host will then address the TSC2000 again, this time
requesting an X-coordinate conversion.
The process is then repeated for Y- and Z-coordinates. The
processes are outlined in Figures 15 through 17.
The time needed to convert any single coordinate under host
control (not including the time needed to send the command
over the SPI bus) is given by:
(5)
t 2.125 s + t N N
1
f
s
COORDINATE PVS AVG BITS
CONV
=µ + • +µ






44.