HT80C51 User Manual
Peripheral Modules – I2C Interface (SIO1)
Handshake Solutions
© Philips Electronics N.V. 2005
Page 65 of 132
application software response
to S1CON
status
code
S1STA
status of the I2C bus
and SIO1 hardware
to/from S1DAT
STA STO
SI
AA
next action taken by SIO1 hard-
ware
08H
A START condition has been
transmitted
Load SLA+W
X
0
0
X
SLA+W will be transmitted;
ACK bit will be received
10H
A repeated START condition
has been transmitted
Load SLA+W or
Load SLA+R
X
X
0
0
0
0
X
X
As above
SLA+W will be transmitted;
SIO1 will be switched to MST/REC mode
18H
SLA+W has been transmit-
ted; ACK has been received
Load data byte or
no S1DAT action or
no S1DAT action or
no S1DAT action
0
1
0
1
0
0
1
1
0
0
0
0
X
X
X
X
Data byte will be transmitted;
ACK bit will be received
Repeated START will be transmitted;
STOP condition will be transmitted;
STO flag will be reset
STOP condition followed by a
START condition will be transmitted;
STO flag will be reset
20H
SLA+W has been transmit-
ted; NOT ACK has been
received
Load data byte or
no S1DAT action or
no S1DAT action or
no S1DAT action
0
1
0
1
0
0
1
1
0
0
0
0
X
X
X
X
Data byte will be transmitted;
ACK bit will be received
Repeated START will be transmitted;
STOP condition will be transmitted;
STO flag will be reset
STOP condition followed by a
START condition will be transmitted;
STO flag will be reset
28H
Data byte in S1DAT has
been transmitted; ACK has
been received
Load data byte or
no S1DAT action or
no S1DAT action or
no S1DAT action
0
1
0
1
0
0
1
1
0
0
0
0
X
X
X
X
Data byte will be transmitted;
ACK bit will be received
Repeated START will be transmitted;
STOP condition will be transmitted;
STO flag will be reset
STOP condition followed by a
START condition will be transmitted;
STO flag will be reset
30H
Data byte in S1DAT has
been transmitted; NOT ACK
has been received
Load data byte or
no S1DAT action or
no S1DAT action or
no S1DAT action
0
1
0
1
0
0
1
1
0
0
0
0
X
X
X
X
Data byte will be transmitted;
ACK bit will be received
Repeated START will be transmitted;
STOP condition will be transmitted;
STO flag will be reset
STOP condition followed by a
START condition will be transmitted;
STO flag will be reset
38H
Arbitration lost in
SLA+R/W or
Data bytes
No S1DAT action or
no S1DAT action
0
1
0
0
0
0
X
X
I2C bus will be released;
not addressed slave will be entered
A START condition will be transmitted
when the bus becomes free
[Table 10] Master Transmitter mode (not available for slave-only version)
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