Silicon Laboratories Si475X Series Programming Manual page 2

AN543
4. Control Interface
2
The Si475x provides an I
In powerdown mode, all circuitry is disabled except for the device control interface. The device comes out of
powerdown mode when the POWER_UP command is written to the command register. Once in powerup mode,
the device accepts additional commands such as tuning. The device will not accept commands while in
powerdown mode, with the exception of the powerup command. If the system controller writes a command other
than POWER_UP when in powerdown mode, the device does not respond, and the command is ignored.
Setting the RSTB pin low places the device in reset mode. In reset mode, all circuitry is disabled including the
device control interface; registers are set to their default settings, and the control bus is disabled.
4.1. 2-Wire Control Interface
Figure 1 and Figure 2 show the 2-wire control interface read and write timing parameters and diagrams,
respectively. Refer to the Si475x data sheet for timing parameter values.
t t
SU:STA HD:STA
70%
SCL
30%
70%
SDA
30%
START
Figure 1. I
SCL
SDA
(Write)
START ADDRESS + R/W
SDA
A6-A0, 1
(Read)
START ADDRESS + R/W
Figure 2. I
2
C-compatible, 2-wire control interface.
t t
LOW HIGH
t t
t
HD:DAT SU:DAT
r:IN
2
C Control Interface Read and Write Timing Parameters
A6-A0, 0
ACK
ACK
2
C Control Interface Read and Write Timing Diagram
t t
t
r:IN f:IN
SP
t
PD:DAT
Command
7-0
DATA ACK
Status
7-0
DATA ACK
Rev. 0.9
t t
SU:STO BUF
t
f:IN,
STOP START
t
f:OUT
Arg1
7-0
DATA ACK
Response
7-0
DATA ACK
STOP
STOP