TSC2000_08 Datasheet, PDF (21/35 Pages) Texas Instruments – PDA ANALOG INTERFACE CIRCUIT

Conversion Controlled by TSC2000 Initiated By
Host Responding to PENIRQ
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, and then write to the A/D
Converter Control register to select one of the touch screen
scan functions. The conversion process then proceeds as
described above, and as outlined in Figures 10 through 14.
The main difference between this mode and the previous
mode is that the host, not the TSC2000, decides when the
touch screen scan begins.
Screen
Touch
Issue Interrupt
PENIRQ
Touch Screen Scan
X and Y
Host Initiated
Is PSM = 1
No _{Go to Host-Controlled}
Conversion
Host Writes A/D
Converter
Control Register
Done
Reset PENIRQ
Start Clock
Turn On Drivers: Y+, Y–
Turn On Drivers: X+, X–
No Is Panel Voltage
Stabilization Done
Yes
Power Up A/D Converter
No Is Panel Voltage
Stabilization Done
Yes
Power Up A/D Converter
Convert Y-Coordinates
No
Is Data
Averaging Done
Yes
Store Y-Coordinates in
Y-Register
Power Down A/D Converter
Is Screen
No
Touched
Yes
Turn Off Clock
Reset PENIRQ and
Scan Trigger
Done
Convert X-Coordinates
No
Is Data
Averaging Done
Yes
Store X-Coordinates
in X-Register
Power Down A/D Converter
Issue Data Available
Yes
Is Screen
Touched
No
Turn Off Clock
Done
FIGURE 10. X- and Y-Coordinate Touch Screen Scan, Initiated by Host.
TSC2000
21
SBAS257
www.ti.com