Datasheet

18
www.ti.com
TSC2000
SBAS257
MSB LSB
BIT 15 BIT 14 BIT 13 BIT 12 BIT 11 BIT 10 BIT 9 BIT 8 BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
10111011XX X XXXXX
TABLE XXIV. Reset Register.
MSB LSB
BIT 15 BIT 14 BIT 13 BIT 12 BIT 11 BIT 10 BIT 9 BIT 8 BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
X X X X X X X X D7 D6 D5 D4 D3 D2 D1 D0
TABLE XXVI. D/A Converter Register.
RESET REGISTER
(PAGE 1, ADDRESS 04
H
)
The TSC2000 has a special register, the RESET register, which
allows a software reset of the device. Writing the code BBXX
H
,
as shown in Table XXIV, to this register will cause the TSC2000
to reset all its registers to their default, power-up values.
Writing any other values to this register will do nothing.
Reading this register or any reserved register will result in
reading back all 1’s, or FFFF
H
.
TSC2000 DATA REGISTERS
The data registers of the TSC2000 hold data results from
conversions or keypad scans, or the value of the D/A converter
output current. All of these registers default to 0000
H
upon reset,
except the D/A converter register, which is set to 0080
H
,
representing the midscale output of the D/A converter.
X, Y, Z
1
, Z
2
, BAT1, BAT2, AUX1, AUX2, TEMP1,
AND TEMP2 REGISTERS
The results of all A/D conversions are placed in the appropri-
ate data register, see Tables III and VIII. The data format of
the result word, R, of these registers is right-justified, as
shown in Table XXV.
D/A CONVERTER DATA REGISTER
(PAGE 0, ADDRESS 0B
H
)
The data to be written to the D/A converter is written into the
D/A converter data register, which is formatted as shown in
Table XXVI.
ZERO REGISTER
(PAGE 0, ADDRESS 10
H
)
This is a reserved data register, but instead of reading all 1’s
(FFFF
H
), when read will return all 0’s (0000
H
).
OPERATION—TOUCH SCREEN MEASUREMENTS
As noted previously in the discussion of the A/D converter,
several operating modes can be used, which allow great
flexibility for the host processor. These different modes will
now be examined.
Conversion Controlled by TSC2000 Initiated at
Touch Detect
In this mode, the TSC2000 will detect when the touch panel is
touched and cause the
PENIRQ line to go LOW. At the same
time, the TSC2000 will start up its internal clock. It will then turn
on the Y-drivers, and after a programmed Panel Voltage
Stabilization time, power up the A/D converter and convert the
Y-coordinate. If averaging is selected, several conversions
may take place; when data averaging is complete, the Y-
coordinate result will be stored in the Y-register.
If the screen is still touched at this time, the X-drivers will be
enabled, and the process will repeat, but instead measuring
the X-coordinate and storing the result in the X-register.
If only X- and Y-coordinates are to be measured, then the
conversion process is complete. See Figure 8 for a flowchart
for this process. The time it takes to go through this process
depends upon the selected resolution, internal conversion
clock rate, averaging selected, panel voltage stabilization
time, and precharge and sense times.
TABLE XXV. Result Data Format.
MSB LSB
BIT 15 BIT 14 BIT 13 BIT 12 BIT 11 BIT 10 BIT 9 BIT 8 BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
0 0 0 0 R11 R10 R9 R8 R7 R6 R5 R4 R3 R2 R1 R0
MSB LSB