CP2120 데이터 시트보기 (PDF) - Silicon Laboratories

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CP2120

SPI TO I2C BRIDGE AND GPIO PORT EXPANDER

Silicon Laboratories 

CP2120

6.5.3. Read Buffer

SPI Master

COMMAND

0x06

Don’t Care

CP2120

Data Byte 0

...

Data Byte N

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

SPI Master

0x02

NUMBER OF

COMMAND WRITE BYTES

NUMBER OF

READ BYTES

SLAVE

ADDRESS+W

DATA WRITE

BYTE 0

...

DATA WRITE

BYTE N

SLAVE

ADDRESS+R

The Read After Write command writes bytes to one I2C slave and then reads bytes from another I2C slave. The

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 I2C slave to which the CP2120

will attempt to write bytes, followed by the data bytes to write. The last byte of the command is the I2C slave from

which the CP2120 will attempt to read bytes.

6.5.5. Write After Write

SPI Master

0x03

COMMAND

NUMBER OF

BYTES 1

NUMBER OF

BYTES 2

SLAVE 1

ADDRESS +W

...

DATA BYTE 1

DATA BYTE N

SLAVE 2

ADDRESS +W

DATA BYTE 1

... DATA BYTE N

The Write After Write command writes to an I2C slave device and then issues another write to a second I2C slave

device. The command begins with the command byte, 0x08, followed by the number of bytes to write to the first I2C

device and the bytes to write to the second I2C device. The SPI master sends the slave address of the first I2C

device and the data bytes to write to the first I2C slave. The SPI Master then sends the slave address of the second

I2C slave device followed by the data bytes to transmit to that slave device.

6.5.6. Write To Multiple Slaves

SPI Master

0x 09

COMMAND

Num Bytes

Num Slaves

Slave0

... Slave N

Data Byte0

... Data Byte N

The Write to Multiple Slaves command allows an SPI Master to write the same data buffer to multiple I2C slaves.

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 I2C transaction of the command.

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Rev. 1.0

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