TFP410

TI PanelBus DIGITAL TRANSMITTER

SLDS145A – OCTOBER 2001 – REVISED JANUARY 2002

22

POST OFFICE BOX 655303

The basic access read cycle consists of the following:

1.

A start condition

2.

A slave write address cycle

3.

A sub-address cycle

4.

A restart condition

5.

A slave read address cycle

6.

Any number of data cycles

7.

A stop condition

The start and stop conditions are shown in Figure 10. The high to low transition of SDA while SCL is high defines

the start condition. The low to high transition of SDA while SCL is high defines the stop condition. Each cycle,

data or address, consists of 8 bits of serial data followed by one acknowledge bit generated by the receiving

device. Thus, each data/address cycle contains 9 bits as shown in Figure 11.

SCL

1

2

3

4

5

6

7

8

9

SDA

1

2

3

4

5

6

7

8

9

2

3

4

5

6

7

1

Slave Address

Sub-Address

Data

Stop

89

acknowledge by pulling the SDA line low during the ninth clock cycle if it decodes the address as its address.

During subsequent sub-address and data cycles, the TFP410 responds with acknowledge as shown in

Figure 12. The sub-address is auto-incremented after each data cycle.

The transmitting device must not drive the SDA signal during the acknowledge cycle so that the receiving device

may drive the SDA signal low. The master indicates a not acknowledge condition (/A) by keeping the SDA signal

high just before it asserts the stop condition (P). This sequence terminates a read cycle as shown in Figure 13.

The slave address consists of 7 bits of address along with 1 bit of read/write information (read = 1, write = 0)

as shown below in Figures 11 and 12. For the TFP410, the selectable slave addresses (including the R/W bit)

using A[3:1]are 0x70, 0x72, 0x74, 0x76, 0x78, 0x7A, 0x7C, and 0x7E for write cycles and 0x71, 0x73, 0x75,

0x77, 0x79, 0x7B, 0x7D, and 0x7F for read cycles.

S

Slave Address

W

A

Sub-Address

A

Data

A

Data

A

P

Where:

From Master

A Acknowledge

From Slave

S Start condition

P Stop Condition