SDA

SCL

1

0

0

1

0

0

A0

R/W

0

0

C3

C2

C1

C0 PD1

M

X

0

START

TSC2017

ACK

TSC2017

ACK

AddressByte

CommandByte

Acquisition

Conversion

STOPor

RepeatedSTART

PD0

TSC2017

SBAS472 – DECEMBER 2009

www.ti.com

START A CONVERTER FUNCTION/WRITE CYCLE

A conversion/write cycle begins when the master issues the address byte containing the slave address of the

TSC2017, with the eighth bit equal to a 0 (R/W = 0), as shown in Table 1. Once the eighth bit has been received,

and the address matches the A0 address input pin setting, the TSC2017 issues an acknowledge.

When the master receives the acknowledge bit from the TSC2017, the master writes the command byte to the

slave (see Table 2). After the command byte is received by the slave, the slave issues another acknowledge bit.

The master then ends the write cycle by issuing a repeated START or a STOP condition, as shown in Figure 31.

Figure 31. Complete I2C Serial Write Transmission

If the master sends additional command bytes after the initial byte, but before sending a STOP or repeated

START condition, the TSC2017 does not acknowledge those bytes.

The input multiplexer channel for the A/D converter is selected when bits C3 through C0 are clocked in. If the

selected channel is an X-,Y-, or Z-position measurement, the appropriate drivers turn on once the acquisition

period begins.

When R/W = 0, the input sample acquisition period starts on the falling edge of SCL when the C0 bit of the

command byte has been latched, and ends when a STOP or repeated START condition has been issued. A/D

conversion starts immediately after the acquisition period. The multiplexer inputs to the A/D converter are

disabled once the conversion period starts. However, if an X-, Y-, or Z-position is being measured, the respective

touch screen drivers remain on during the conversion period. A complete write cycle is shown in Figure 31.

26

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