cp2120 Silicon Laboratories, cp2120 Datasheet - Page 18

• Manufacturer Part Number: cp2120
• Description: Single Chip Spi To I2c Transfer Integrated Clock; No External Clock Required On-chip Voltage Monitor
• Manufacturer: Silicon Laboratories

CP2120
6.5.3. Read Buffer
The Read Buffer command retrieves bytes from the CP2120's data buffer. The command begins with the command
byte, 0x06. After the command byte, the SPI Master must transmit a single byte of data, which is ignored by the
CP2120. After receiving the ignored byte of data, the CP2120 transmits data bytes across the MISO pin.
It is recommended that the SPI Master read the RXBUFF Internal Register to determine how many bytes are
stored in the CP2120's buffer before issuing a Read Buffer command. If the SPI Master attempts to retrieve more
bytes than the buffer contains, the CP2120 will signal the error in I2CSTAT. If an SPI Master attempts to retrieve
fewer bytes than are stored in the data buffer, all bytes left in the buffer will be deleted when the Read Buffer
command terminates.
6.5.4. Read After Write
The Read After Write command writes bytes to one I
SPI Master calls this command by first sending the command byte, 0x02, then the number of bytes to write (1 to
255) and bytes to read (1 to 255). These bytes are followed by the address of the I
will attempt to write bytes, followed by the data bytes to write. The last byte of the command is the I
which the CP2120 will attempt to read bytes.
6.5.5. Write After Write
The Write After Write command writes to an I
device. The command begins with the command byte, 0x08, followed by the number of bytes to write to the first I
device and the bytes to write to the second I
device and the data bytes to write to the first I
I
6.5.6. Write To Multiple Slaves
The Write to Multiple Slaves command allows an SPI Master to write the same data buffer to multiple I
The command begins with the command byte, 0x09, followed by the size of the data buffer (0 to 255), followed by
the number of slaves (0 to 254). Next, the list of slave addresses is transmitted. Following that, the data buffer to
write to each slave is transmitted. The combined size of the slave address list and the data buffer should not
exceed 255 bytes. The I2CSTAT Internal Register shows the results from the last I
18
2
SPI Master
SPI Master
SPI Master
C slave device followed by the data bytes to transmit to that slave device.
COMMAND
0x03
COMMAND
0x 09
COMMAND
0x02
NUMBER OF
BYTES 1
SPI Master
CP2120
Num Bytes
WRITE BYTES
NUMBER OF
NUMBER OF
BYTES 2
Num Slaves
COMMAND
READ BYTES
NUMBER OF
0x06
ADDRESS +W
SLAVE 1
2
2
2
C slave. The SPI Master then sends the slave address of the second
C slave device and then issues another write to a second I
C device. The SPI master sends the slave address of the first I
DATA BYTE 1
Don’t Care
Slave 0
Rev. 0.3
ADDRESS+W
2
C slave and then reads bytes from another I
SLAVE
...
...
Data Byte 0
DATA BYTE N
DATA WRITE
BYTE 0
Slave N
ADDRESS +W
...
SLAVE 2
...
2
C transaction of the command.
2
Data Byte N
Data Byte 0
C slave to which the CP2120
DATA BYTE 1
DATA WRITE
BYTE N
...
...
2
2
ADDRESS+R
C slave. The
C slave from
SLAVE
2
Data Byte N
DATA BYTE N
C slaves.
2
C slave
2
2
C
C