TSC2003
16
SBAS162G
www.ti.com
Address Byte
The address byte, as shown in Figure 10, is the first byte
received following the START condition from the master
device. The first five bits (MSBs) of the slave address are
factory preset to 10010. The next two bits of the address byte
are the device select bits: A1 and A0. Input pins (A1-A0) on
the TSC2003 determine these two bits of the device address
for a particular TSC2003. Therefore, a maximum of four
devices with the same preset code can be connected on the
same bus at one time.
FIGURE 10. Address Byte.
1
0
1
0
A1
A0
R/W
MSB
LSB
FIGURE 11. Command Byte.
C3
C2
C1
C0
PD1
PD0
M
X
MSB
LSB
C3
C2
C1
C0
FUNCTION
INPUT to ADC
X-DRIVERS
Y-DRIVERS
REFERENCE MODE
0
Measure TEMP0
TEMP0
OFF
Single-Ended
0
1
Measure VBAT1
VBAT1
OFF
Single-Ended
0
1
0
Measure IN1
IN1
OFF
Single-Ended
0
1
Reserved
––
–
Single-Ended
0
1
0
Measure TEMP1
TEMP1
OFF
Single-Ended
0
1
0
1
Measure VBAT2
VBAT2
OFF
Single-Ended
0
1
0
Measure IN2
IN2
OFF
Single-Ended
0
1
Reserved
––
–
Single-Ended
1
0
Activate X– Drivers
–
ON
OFF
Differential
1
0
1
Activate Y– Drivers
–
OFF
ON
Differential
1
0
1
0
Activate Y+, X– Drivers
–
X– ON
Y+ ON
Differential
1
0
1
Reserved
––
–
Differential
1
0
Measure X Position
Y+
ON
OFF
Differential
1
0
1
Measure Y Position
X+
OFF
ON
Differential
1
0
Measure Z1 Position
X+
X– ON
Y+ ON
Differential
1
Measure Z2 Position
Y–
X– ON
Y+ ON
Differential
TABLE I. Possible Input Configurations.
The internal reference voltage can be turned ON or OFF
independently of the A/D converter. This can allow extra time
for the internal reference voltage to settle to its final value prior
to making a conversion. Make sure to allow this extra wake-
up time if the internal reference was powered down. Also note
that the status of the internal reference power down is latched
into the part (internally) when a STOP or repeated START
occurs at the end of a command byte (see Figures 12 and 14).
Therefore, in order to turn the internal reference OFF, an
additional write to the TSC2003, with PD1 = 0, is required after
the channel has been converted.
It is recommended to set PD0 = 0 in each command byte to get
the lowest power consumption possible. If multiple X-, Y-, and
Z-position measurements will be done one right after another,
such as when averaging, PD0 =1 will leave the touch screen
drivers on at the end of each conversion cycle.
M: Mode bit. If M is 0, the TSC2003 is in 12-bit mode. If
M is 1, 8-bit mode is selected.
X: Don’t care.
The A1-A0 Address Inputs can be connected to VDD or digital
ground. The last bit of the address byte (R/W) defines the
operation to be performed. When set to a “1”, a read
operation is selected; when set to a “0”, a write operation is
selected. Following the START condition, the TSC2003
monitors the SDA bus and checks the device type identifier
being transmitted. Upon receiving the 10010 code, the ap-
propriate device select bits, and the R/W bit, the slave device
outputs an acknowledge signal on the SDA line.
Command Byte
The TSC2003’s operating mode is determined by a com-
mand byte, which is shown in Figure 11.
PD1
PD0
PENIRQ
DESCRIPTION
0
Enabled
Power-Down Between Conversions
0
1
Disabled
Internal reference OFF, ADC(1) ON
1
0
Enabled
Internal reference ON, ADC(1) OFF
1
Disabled
Internal reference ON, ADC(1) ON
NOTE: (1) ADC = Analog-to Digital Converter.
TABLE II. Power-Down Bit Functions.
The bits in the device command byte are defined as follows:
C3-C0: Configuration bits. These bits set the input multi-
plexer address and functions that the TSC2003 will per-
form, as shown in Table I.
PD1-PD0: Power-down bits. These two bits select the
power-down mode that the TSC2003 will be in after the
current command completes, as shown in Table II.
When the TSC2003 powers up, the power-down mode bits
need to be written to ensure that the part is placed into the
desired mode to achieve lowest power. Therefore, immedi-
ately after power-up, a command byte should be sent which
sets PD1 = PD0 = 0, so that the device will be in the lowest
power mode, powering down between conversions.
Start A Conversion/Write Cycle
A Conversion/Write Cycle begins when the master issues the
address byte containing the slave address of the TSC2003,
with the eighth bit equal to a 0 (R/W = 0), as shown in Figure
10. Once the eighth bit has been received, and the address
matches the A1-A0 address input pin setting, the TSC2003
issues an acknowledge.