TSC2003

15

SBAS162D

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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

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

0

0

0

Measure TEMP0

TEMP0

OFF

OFF

Single-Ended

0

0

0

1

OFF

OFF

Single-Ended

0

0

1

0

Measure IN1

IN1

OFF

OFF

Single-Ended

0

0

1

1

Reserved

––

–

Single-Ended

0

1

0

0

Measure TEMP1

TEMP1

OFF

OFF

Single-Ended

0

1

0

1

OFF

OFF

Single-Ended

0

1

1

0

Measure IN2

IN2

OFF

OFF

Single-Ended

0

1

1

1

Reserved

––

–

Single-Ended

1

0

0

0

Activate X– Drivers

–

ON

OFF

Differential

1

0

0

1

Activate Y– Drivers

–

OFF

ON

Differential

1

0

1

0

Activate Y+, X– Drivers

–

X– ON

Y+ ON

Differential

1

0

1

1

Reserved

––

–

Differential

1

1

0

0

Measure X Position

Y+

ON

OFF

Differential

1

1

0

1

Measure Y Position

X+

OFF

ON

Differential

1

1

1

0

X+

X– ON

Y+ ON

Differential

1

1

1

1

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.

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

0

Enabled

Power-Down Between Conversions

0

1

Disabled

1

0

Enabled

1

1

Disabled

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.