Handshake Solutions
HT80C51 User Manual
Peripheral Modules – I2C Interface (SIO1)
Page 66 of 132
© Philips Electronics N.V. 2005
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+R
X
0
0
X
SLA+W will be transmitted;
ACK bit will be received
10H
A repeated START condition
has been transmitted
Load SLA+R or
Load SLA+W
X
X
0
0
0
0
X
X
As above
SLA+W will be transmitted;
SIO1 will be switched to MST/TRX mode
38H
Arbitration
lost
in
NOT ACK bit
No S1DAT action or
no S1DAT action
0
1
0
0
0
0
X
X
I2C bus will be released;
SIO1 will enter slave mode
A START condition will be transmitted
when the bus becomes free
40H
SLA+R has been transmitted;
ACK has been received
No S1DAT action or
no S1DAT action
0
0
0
0
0
0
0
1
Data byte will be received;
NOT ACK bit will be returned
Data byte will be received;
ACK bit will be returned
48H
SLA+R has been transmitted;
NOT ACK has been received
No S1DAT action or
no S1DAT action or
no S1DAT action
1
0
1
0
1
1
0
0
0
X
X
X
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
50H
Data byte has been received;
ACK has been returned
Read data byte or
read data byte
0
0
0
0
0
0
0
1
Data byte will be received;
NOT ACK bit will be returned
Data byte will be received;
ACK bit will be returned
58H
Data byte has been received;
NOT ACK has been returned
Read data byte or
read data byte or
read data byte
1
0
1
0
1
1
0
0
0
X
X
X
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
[Table 11] Master Receiver Mode (not available for slave-only version)
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