C8051F300/1/2/3/4/5
Rev. 2.9
127
13.6. SMBus Status Decoding
The current SMBus status can be easily decoded using the SMB0CN register. In the table below, STATUS
VECTOR refers to the four upper bits of SMB0CN: MASTER, TXMODE, STA, and STO. Note that the
shown response options are only the typical responses; application-specific procedures are allowed as
long as they conform with the SMBus specification. Highlighted responses are allowed but do not conform
to the SMBus specification.
Table 13.4. SMBus Status Decoding
M
ode
Values Read
Current SMbus State
Typical Response Options
Values
Written
St
a
tu
s
Ve
c
to
r
AC
KRQ
ARB
LOST
AC
K
ST
A
ST
O
AC
K
M
a
st
er T
ran
s
m
it
te
r
1110
0
0
X A master START was generated. Load slave a R/W
into SMB0DAT.
0
0
X
1100
0
0
0 A master data or address byte
was transmitted; NACK received.
Set STA to restart transfer.
1
0
X
Abort transfer.
0
1
X
0
0
1 A master data or address byte
was transmitted; ACK received.
Load next data byte into
SMB0DAT
0
0
X
End transfer with STOP
0
1
X
End transfer with STOP and
start another transfer.
1
1
X
Send repeated START
1
0
X
Switch to Master Receiver
Mode (clear SI without writ-
ing new data to SMB0DAT).
0
0
X
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