User Manual

Chapter 2 _______________________________________________________________ I2C Interface
VAISALA _____________________________________________________________________ 7
Examples of Communication Flow
The basic data transfer communication flows are presented in the
following figures. Each arrow represents an I
2
C read or write operation
The examples are simplified presentations. For actual message content,
see section Commandson page 11.
For example, Figure 3 below shows the following message sequence:
1. The master invokes the Get_Parameter command to read the RH
parameter using an I
2
C write operation. This command prepares the
slave to wait for a read operation from the master.
2. The master begins an I
2
C read operation to read the results of the
Get_Parameter RH command. The slave sends the requested RH
result and an ACK signal to the master.
1401-020
Figure 3 Get_Parameter with ACK
1401-032
Figure 4 Set_Parameter with ACK
Master
Slave
Get_Parameter,RH_ID
I2C write
Get_Parameter,RH_ID,54.32, ACK
I2C read
Master
Slave
Set_Parameter,Pressure_ID,1013.25
I2C Write
Set_Parameter,Pressure_ID,ACK
I2C Read