Datasheet

HOST
SER
or
DES
SCL
SDA
4.7k 4.7k
10k
R
CAD
SCL
SDA
To other
Devices
CAD
1.8V
V
DDIO
DS92LX2121, DS92LX2122
SNLS330I –MAY 2010–REVISED APRIL 2013 www.ti.com
Figure 28. Serial Control Bus Connection
SLAVE CLOCK STRETCHING
In order to communicate and synchronize with remote devices on the I
2
C bus through the bi-directional control
channel, slave clock stretching must be supported by the I
2
C master controller/host device. The chipset utilizes
bus clock stretching (holding the SCL line low) during data transmission; where the I2C slave pulls the SCL line
low on the 9th clock of every I
2
C data transfer (before the ACK signal). The slave device will not control the clock
and only stretches it until the remote peripheral has responded; which is typically in the order of 12 μs (typical).
CAD PIN ADDRESS DECODER
The CAD pin is used to decode and set the physical slave address of the Serializer/Deserializer (I
2
C only) to
allow up to six devices on the bus using only a single pin. The pin sets one of six possible addresses for each
Serializer/Deserializer device. The pin must be pulled to VDD (1.8V, NOT VDDIO)) with a 10 kΩ resistor and a
pull down resistor (RID) of the recommended value to set the physical device address. The recommended
maximum resistor tolerance is 0.1% worst case (0.2% total tolerance).
Table 3. DS92LX2121 RID Resistor Values
CAD Values - DS92LX2121 Ser
Resistor RID kΩ Address 7'b Address 8'b 0 appended (WRITE)
0 7b' 101 1000 (h'58) 8b' 1011 0000 (h'B0)
GND
2.0k 7b' 101 1001 (h'59) 8b' 1011 0010 (h'B2)
4.7k 7b' 101 1010 (h'5A) 8b' 1011 0100 (h'B4)
8.2k 7b' 101 1011 (h'5B) 8b' 1011 0110 (h'B6)
12.1k 7b' 101 1100 (h'5C) 8b' 1011 1000 (h'B8)
39.0k 7b' 101 1110 (h'5E) 8b' 1011 1100 (h'BC)
Table 4. DS92LX2122 RID Resistor Values
CAD Values - DS92LX2122 Des
Resistor RID kΩ Address 7'b Address 8'b 0 appended (WRITE)
0 7b' 110 0000 (h'60) 8b' 1100 0000 (h'C0)
GND
2.0k 7b' 110 0001 (h'61) 8b' 1100 0010 (h'C2)
4.7k 7b' 110 0010 (h'62) 8b' 1100 0100 (h'C4)
8.2k 7b' 110 0011 (h'63) 8b' 1101 0110 (h'C6)
12.1k 7b' 110 0100 (h'64) 8b' 1101 1000 (h'C8)
39.0k 7b' 110 0110 (h'66) 8b' 1100 1100 (h'CC)
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