TSC2000 datasheet(26/34 Pages) TI

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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

Start Clock

Reset PENIRQ

Is Panel Voltage

Stabilization Done

Turn On Drivers: X+, X–

Yes

Is Data

Averaging Done

Convert X-Coordinates

Start Clock

Power Up A/D Converter

Is PSM = 1

Are Drivers On

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)

2.125 s + t

COORDINATE

PVS

AVG

BITS

CONV

=µ

•









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