Si5345-44-42-D-RM
Rev. 1.0
53
9.1. I
2
C Interface
When in I
2
C mode, the serial interface operates in slave mode with 7-bit addressing and can operate in Standard-
Mode (100 kbps) or Fast-Mode (400 kbps) and supports burst data transfer with auto address increments. The I
2
C
bus consists of a bidirectional serial data line (SDA) and a serial clock input (SCL) as shown in Figure 26. Both the
SDA and SCL pins must be connected to a supply via an external pull-up (4.7 k
) as recommended by the I
2
C
specification as shown in Figure 24. Two address select bits (A0, A1) are provided allowing up to four Si5345/44/42
devices to communicate on the same bus. This also allows four choices in the I
2
C address for systems that may
have other overlapping addresses for other I
2
C devices.
Figure 24. I
2
C Configuration
The 7-bit slave device address of the Si5345/44/42 consists of a 5-bit fixed address plus 2 pins which are
selectable for the last two bits, as shown in Figure 25.
Figure 25. 7-bit I
2
C Slave Address Bit-Configuration
Data is transferred MSB first in 8-bit words as specified by the I
2
C specification. A write command consists of a 7-
bit device (slave) a a write bit, an 8-bit register address, and 8 bits of data as shown in Figure 28. A write
burst operation is also shown where subsequent data words are written using to an auto-incremented address.
SDA
SCLK
Si5345/44/42
I2C_SEL
VDD
VDDI2C
To I
2
C Bus
or Host
A0
A1
LSBs of I
2
C
Address
I
2
C
Slave Address
1
1
0
1
0
A0
0
1
2
3
4
5
6
A1