Intel
®
81341 and 81342—I
2
C Bus Interface Units
Intel
®
81341 and 81342 I/O Processors
Developer’s Manual
December 2007
924
Order Number: 315037-002US
When the 81341 and 81342 needs to read data, the I
2
C unit transitions from slave-
receive mode to master-transmit mode to transmit the start address and immediately
following the ACK pulse transitions to master-receive mode to wait for the reception of
the read data from the slave device (see
). It is also possible to have
multiple transactions during an I
2
C operation such as transitioning from master-receive
to master-transmit through a repeated start or Data Chaining (see
shows the wave forms of
SDA
and
SCL
for a complete data transfer.
Figure 148. Master-Receiver Read from Slave-Transmitter
Figure 149. Master-Receiver Read from Slave-Transmitter / Repeated Start /Master-
Transmitter Write to Slave-Receiver
Figure 150. A Complete Data Transfer
Master to Slave
Slave to Master
START
Slave
Address
R/W#
1
ACK
Data
Byte
ACK
Data
Byte
STOP
N Bytes + ACK
ACK
Default
Slave-Receive
Mode
First Byte
Read
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Start Slave
R
/W
#
1
Data
Byte
Data
Byte
N Bytes + ACK
Read
Sr
Slave
R
/W
#
0
A
C
K Data
Byte
Data
Byte
S
TO
P
N Bytes + ACK
Write
Address
Address
Master to Slave
Slave to Master
Repeated
Start
Data Chaining
A
C
K
A
C
K
A
C
K
A
C
K
A
C
K
B6290-01
SDA
SCL
Start
Condition
Address R/W# ACK
Data
ACK
Data
1-7
8
9
8
9
8
9
1-7
1-7
ACK
Stop
Condition
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B6291-01