C8051F300_08 Datasheet, PDF (122/179 Pages) Silicon Laboratories – Mixed Signal ISP Flash MCU Family

C8051F300/1/2/3/4/5
13.4.3. Data Register
The SMBus Data register SMB0DAT holds a byte of serial data to be transmitted or one that has just been
received. Software may safely read or write to the data register when the SI flag is set. Software should not
attempt to access the SMB0DAT register when the SMBus is enabled and the SI flag is cleared to logic 0,
as the interface may be in the process of shifting a byte of data into or out of the register.
Data in SMB0DAT is always shifted out MSB first. After a byte has been received, the first bit of received
data is located at the MSB of SMB0DAT. While data is being shifted out, data on the bus is simultaneously
being shifted in. SMB0DAT always contains the last data byte present on the bus. In the event of lost arbi-
tration, the transition from master transmitter to slave receiver is made with the correct data or address in
SMB0DAT.
SFR Definition 13.3. SMB0DAT: SMBus Data
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset Value
00000000
Bit7
Bit6
Bit5
Bit4
Bit3
Bit2
Bit1
Bit0 SFR Address:
0xC2
Bits7–0:
SMB0DAT: SMBus Data.
The SMB0DAT register contains a byte of data to be transmitted on the SMBus serial inter-
face or a byte that has just been received on the SMBus serial interface. The CPU can read
from or write to this register whenever the SI serial interrupt flag (SMB0CN.0) is set to logic
one. The serial data in the register remains stable as long as the SI flag is set. When the SI
flag is not set, the system may be in the process of shifting data in/out and the CPU should
not attempt to access this register.
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