Si5341/40
Preliminary Rev. 0.9
35
Serial Interface
I2C_SEL
39
38
I
I2C Select
This pin selects the serial interface mode as I
2
C (I2C_SEL = 1) or
SPI (I2C_SEL = 0). This pin is internally pulled high. See Note 2.
SDA/SDIO
18
13
I/O
Serial Data Interface
This is the bidirectional data pin (SDA) for the I
2
C mode, or the
bidirectional data pin (SDIO) in the 3-wire SPI mode, or the input
data pin (SDI) in 4-wire SPI mode. When in I
2
C mode, this pin
must be pulled-up using an external resistor of at least 1 k
. No
pull-up resistor is needed when is SPI mode. See Note 2.
A1/SDO
17
15
I/O
Address Select 1/Serial Data Output
In I
2
C mode this pin functions as the A1 address input pin. In 4-
wire SPI mode this is the serial data output (SDO) pin. See Note
2.
SCLK
16
14
I
Serial Clock Input
This pin functions as the serial clock input for both I
2
C and SPI
modes. When in I
2
C mode, this pin must be pulled-up using an
external resistor of at least 1 k
. No pull-up resistor is needed
when in SPI mode. See Note 2.
A0/CS
19
16
I
Address Select 0/Chip Select
This pin functions as the hardware controlled address A0 in I
2
C
mode. In SPI mode, this pin functions as the chip select input
(active low). This pin is internally pulled-up. See Note 2.
Table 17. Si5341/40 Pin Descriptions (Continued)
Pin Name
Pin Number
Pin Type
1
Function
Notes:
1.
I = Input, O = Output, P = Power.
2.
The IO_VDD_SEL control bit (0x0943 bit 0) selects 3.3 V or 1.8 V operation.
3.
The voltage on the VDDS pin(s) determines 3.3 V or 1.8 V operation.