ISL6423B Datasheet, PDF (11/16 Pages) Intersil Corporation – Single Output LNB Supply and Control Voltage Regulator with I2C Interface for Advanced Satellite Set-Top Box Designs

Byte Format
Every byte put on the SDA line must be eight bits long. The
number of bytes that can be transmitted per transfer is
unrestricted. Each byte has to be followed by an
acknowledge bit. Data is transferred with the most significant
bit first (MSB).
Acknowledge
The master (microprocessor) puts a resistive HIGH level on
the SDA line during the acknowledge clock pulse (Figure 6).
The peripheral that acknowledges has to pull down (LOW)
the SDA line during the acknowledge clock pulse, so that the
SDA line is stable LOW during this clock pulse. (Of course,
set-up and hold times must also be taken into account.)
The peripheral which has been addressed has to generate
an acknowledge after the reception of each byte, otherwise
the SDA line remains at the HIGH level during the ninth
clock pulse time. In this case, the master transmitter can
generate the STOP information in order to abort the transfer.
The ISL6423B will not generate the acknowledge if the
POWER OK signal from the UVLO is LOW.
SCL
SDA
START
1
2
8
9
MSB
ACKNOWLEDGE
FROM SLAVE
FIGURE 6. ACKNOWLEDGE ON THE I²C BUS
Transmission Without Acknowledge
Avoiding detection of the acknowledgement, the
microprocessor can use a simpler transmission; it waits one
clock without checking the slave acknowledging, and sends
the new data.
This approach, though, is less protected from error and
decreases the noise immunity.
ISL6423B Software Description
Interface Protocol
The interface protocol is comprised of the following, as
shown below in Table 2:
• A start condition (S)
• A chip address byte (MSB on left; the LSB bit determines
read (1) or write (0) transmission) (the assigned I²C slave
address for the ISL6423B is 0001 0XXX)
• A sequence of data (1 byte + Acknowledge)
• A stop condition (P)
TABLE 2. INTERFACE PROTOCOL
S 0 0 0 1 0 A1 A0 R/W ACK Data (8 bits) ACK P
System Register Format
• R, W = Read and Write bit
• R = Read-only bit
All bits reset to 0 at Power-On
TABLE 3. STATUS REGISTER (SR1)
R, W R, W R, W R
R
R
R
SR1H SR1M SR1L OTF CABF OUVF OLF
R
BCF
TABLE 4. TONE REGISTER (SR2)
R, W R, W R, W R, W R, W R, W R, W
SR2H SR2M SR2L ENT MSEL TTH X
R, W
X
TABLE 5. COMMAND REGISTER (SR3)
R, W R, W R, W R, W R, W R, W R, W R, W
SR3H SR3M SR3L DCL VSPEN X ISELH ISELL
TABLE 6. CONTROL REGISTER (SR4)
R, W R, W R, W R, W R, W R, W R, W R, W
SR4H SR4M SR4L EN
VTOP VBOT
Transmitted Data (I²C bus WRITE mode)
When the R/W bit in the chip is set to 0, the main
microprocessor can write on the system registers (SR2 thru
SR4) of the ISL6423B via I²C bus. These will be written by
the microprocessor as shown below. The spare bits of
registers can be used for other functions.
11
FN6412.1
April 10, 2007