Datasheet

SDA
SCL
S P
START condition, or
START repeat condition
STOP condition
HOST
SER
or
DES
SCL
SDA
4.7k 4.7k
10 k
R
ID
SCL
SDA
To other
Devices
ID[X]
1.8V
V
DDIO
DS92LV2421, DS92LV2422
SNLS321B –MAY 2010–REVISED APRIL 2013 www.ti.com
Figure 30. Serial Control Bus Connection
The third pin is the ID[X] pin. This pin sets one of five possible device addresses. Three different connections are
possible. The pin may be tied to ground. The pin may be pulled to V
DD
(1.8V, NOT V
DDIO
)) with a 10 kΩ resistor.
Or a 10 kΩ pull up resistor (to V
DD
1.8V, NOT V
DDIO
)) and a pull down resistor of the recommended value to set
other three possible addresses may be used. See Table 11 for the Ser and Table 12 for the Des.
The Serial Bus protocol is controlled by START, START-Repeated, and STOP phases. A START occurs when
SCL transitions Low while SDA is High. A STOP occurs when SDA transition High while SCL is also HIGH. See
Figure 31
Figure 31. START and STOP Conditions
To communicate with a remote device, the host controller (master) sends the slave address and listens for a
response from the slave. This response is referred to as an acknowledge bit (ACK). If a slave on the bus is
addressed correctly, it Acknowledges (ACKs) the master by driving the SDA bus low. If the address doesn't
match a device's slave address, it Not-acknowledges (NACKs) the master by letting SDA be pulled High. ACKs
also occur on the bus when data is being transmitted. When the master is writing data, the slave ACKs after
every data byte is successfully received. When the master is reading data, the master ACKs after every data
byte is received to let the slave know it wants to receive another data byte. When the master wants to stop
reading, it NACKs after the last data byte and creates a stop condition on the bus. All communication on the bus
begins with either a Start condition or a Repeated Start condition. All communication on the bus ends with a Stop
condition. A READ is shown in Figure 32 and a WRITE is shown in Figure 33.
If the Serial Bus is not required, the three pins may be left open (NC).
Table 11. ID[x] Resistor Value – DS92LV2421 Ser
Resistor Address Address
RID kΩ 7'b 8'b
0 appended
(WRITE)
0.47 7b' 110 1001 (h'69) 8b' 1101 0010 (h'D2)
2.7 7b' 110 1010 (h'6A) 8b' 1101 0100 (h'D4)
8.2 7b' 110 1011 (h'6B) 8b' 1101 0110 (h'D6)
Open 7b' 110 1110 (h'6E) 8b' 1101 1100 (h'DC)
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