AN355: Si5040 Two-Byte Read I2C Protocol

AN355
Si5040 TW O -B YTE R EAD I 2 C P ROTOCOL
1. Introduction
Silicon Labs has found that some MCUs do not support the normal I2C master read protocol of a repeated start.
Fortunately, the Si5040 can support an alternate 2-command read sequence. This protocol should only be used in
a single-master bus since the master has to release the bus between commands.
S Slave Address
0
A Byte Address A
S
Slave Address 1
A
Data
A
Data
N P
Figure 1. Normal I2C Repeated Start Read Sequence
S Slave Address
0
A Byte Address A
S Slave Address
1
A
Data
A
P
Data
N P
Figure 2. Alternate 2 Command I2C Read Sequence
From master to slave
From slave to master
1 – Read
0 – Write
A – Acknowledge (SDA LOW)
N – Not Acknowledge (SDA HIGH).
Required after the last data byte to signal the end of the read comand to the slave.
S – START condition
P – STOP condition
Rev. 0.1 10/08
Copyright © 2008 by Silicon Laboratories
AN355
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