SI4707-B20 Datasheet, PDF (17/30 Pages) Silicon Laboratories – WEATHER BAND AND SAME DATA RECEIVER

Si4707-B20
4.8.1. 2-Wire Control Interface Mode
When selecting 2-wire mode, the user must ensure that
SCLK is high during the rising edge of RST, and stays
high until after the first start condition. Also, a start
condition must not occur within 300 ns before the rising
edge of RST.
The 2-wire bus mode uses only the SCLK and SDIO
pins for signaling. A transaction begins with the START
condition, which occurs when SDIO falls while SCLK is
high. Next, the user drives an 8-bit control word serially
on SDIO, which is captured by the device on rising
edges of SCLK. The control word consists of a 7-bit
device address, followed by a read/write bit (read = 1,
write = 0). The Si4707 acknowledges the control word
by driving SDIO low on the next falling edge of SCLK.
Although the Si4707 will respond to only a single device
address, this address can be changed with the SEN pin
(note that the SEN pin is not used for signaling in 2-wire
mode). When SEN = 0, the 7-bit device address is
0010001b. When SEN = 1, the address is 1100011b.
For write operations, the user then sends an 8-bit data
byte on SDIO, which is captured by the device on rising
edges of SCLK. The Si4707 acknowledges each data
byte by driving SDIO low for one cycle, on the next
falling edge of SCLK. The user may write up to eight
data bytes in a single 2-wire transaction. The first byte is
a command, and the next seven bytes are arguments.
For read operations, after the Si4707 has
acknowledged the control byte, it will drive an 8-bit data
byte on SDIO, changing the state of SDIO on the falling
edge of SCLK. The user acknowledges each data byte
by driving SDIO low for one cycle, on the next falling
edge of SCLK. If a data byte is not acknowledged, the
transaction will end. The user may read up to 16 data
bytes in a single 2-wire transaction. These bytes contain
the response data from the Si4707.
A 2-wire transaction ends with the STOP condition,
which occurs when SDIO rises while SCLK is high.
For details on timing specifications and diagrams, refer
to Table 5, “2-Wire Control Interface Characteristics” on
page 7; Figure 2, “2-Wire Control Interface Read and
Write Timing Parameters,” on page 8, and Figure 3, “2-
Wire Control Interface Read and Write Timing Diagram,”
on page 8.
4.8.2. 3-Wire Control Interface Mode
When selecting 3-wire mode, the user must ensure that
a rising edge of SCLK does not occur within 300 ns
before the rising edge of RST.
The 3-wire bus mode uses the SCLK, SDIO, and SEN_
pins. A transaction begins when the user drives SEN
low. Next, the user drives a 9-bit control word on SDIO,
which is captured by the device on rising edges of
SCLK. The control word consists of a 3-bit device
address (A7:A5 = 101b), a read/write bit (read = 1, write
= 0), and a 5-bit register address (A4:A0).
For write operations, the control word is followed by a
16-bit data word, which is captured by the device on
rising edges of SCLK.
For read operations, the control word is followed by a
delay of one-half SCLK cycle for bus turn-around. Next,
the Si4707 will drive the 16-bit read data word serially
on SDIO, changing the state of SDIO on each rising
edge of SCLK.
A transaction ends when the user sets SEN high, then
pulses SCLK high and low one final time. SCLK may
either stop or continue to toggle while SEN is high.
In 3-wire mode, commands are sent by first writing each
argument to register(s) 0xA1–0xA3, then writing the
command word to register 0xA0. A response is
retrieved by reading registers 0xA8–0xAF.
For details on timing specifications and diagrams, refer
to Table 6, “3-Wire Control Interface Characteristics,” on
page 9; Figure 4, “3-Wire Control Interface Write Timing
Parameters,” on page 9, and Figure 5, “3-Wire Control
Interface Read Timing Parameters,” on page 9.
4.8.3. SPI Control Interface Mode
When selecting SPI mode, the user must ensure that a
rising edge of SCLK does not occur within 300 ns
before the rising edge of RST.
SPI bus mode uses the SCLK, SDIO, and SEN pins for
read/write operations. The system controller can
choose to receive read data from the device on either
SDIO or GPO1. A transaction begins when the system
controller drives SEN = 0. The system controller then
pulses SCLK eight times, while driving an 8-bit control
byte serially on SDIO. The device captures the data on
rising edges of SCLK. The control byte must have one
of five values:
 0x48 = write a command (controller drives 8
additional bytes on SDIO).
 0x80 = read a response (device drives one
additional byte on SDIO).
 0xC0 = read a response (device drives 16 additional
bytes on SDIO).
Rev. 0.8
17