TSC2017

SBAS472 – DECEMBER 2009

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DIGITAL INTERFACE

ADDRESS BYTE

The TSC2017 has a 7-bit slave address word. The first six bits (MSBs) of the slave address are factory-preset to

comply with the I2C standard for A/D converters and are always set at '100100'. The logic state of the address

input pin (A0) determines the LSB of the device address to activate communication. Therefore, a maximum of

two devices with the same preset code can be connected on the same bus at one time.

The A0 address input is read whenever an address byte is received, and should be connected to the supply pin

(VDD/REF) or the ground pin (GND). The slave address is latched into the TSC2017 on the falling edge of SCL

after the read/write bit has been received by the slave.

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 TSC2017

monitors the SDA bus, checking the device type identifier being transmitted. The slave device outputs an

acknowledge signal on the SDA line upon receiving the '100100' code, the appropriate device select bit, and the

R/W bit.

Table 1. I2C Slave Address Byte

MSB

LSB

D7

D6

D5

D4

D3

D2

D1

D0

1

0

0

1

0

0

A0

R/W

Bit D0: R/W

1: I2C master read from TSC (I2C read addressing).

0: I2C master write to TSC (I2C write addressing).

COMMAND BYTE

Table 2. Command Byte Definition (Excluding the Setup Command)(1)

BIT

NAME

DESCRIPTION

D7-D4

C3-C0

All Converter Function Select bits as detailed in Table 3, except for the setup command ('1011').

00: Power down between cycles. PENIRQ enabled.

01: A/D converter on. PENIRQ disabled.

D3-D2

PD1-PD0

10: A/D converter off. PENIRQ enabled.

11: A/D converter on. PENIRQ disabled.

0: 12-bit (Lower speed referred to as the 2MHz clock).

D1

M

1: 8-bit (Higher speed referred to as the 4MHz clock).

D0

X

Don't care.

(1)

The command byte definition for the setup command is shown in Table 4.

Bits D7-D4: C3-C0—Converter function select bits. These bits select the input to be converted and the converter

function to be executed, activate the drivers, and configure the PENIRQ pull-up resistor (RIRQ). Table 3 lists the

possible converter functions.

Bits D3-D2: PD1-PD0—Power-down bits. These two bits select the power-down mode that the TSC2017 will be

in after the current command completes, as shown in Table 2.

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.

Bit D1: M—Mode bit. If M = 0, the TSC2017 is in 12-bit mode. If M = 1, 8-bit mode is selected.

Bit D0: X—Don’t care.

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