Vaisala GMP231 - Manual (Page 56)

User's Guide _______________________________________________________________________
54 ___________________________________________________________________ M211501EN-C
1403-146
Figure 13 GMP231 State Machine
Examples of Communication Flow
The basic data transfer communication flows are presented in the figures
below. Each arrow represents an I
2
C read or write operation The
examples are simplified presentations. For actual message content, see
section Commands on page 58.
For example, Figure 14 below shows the following message sequence:
1. The master invokes the Get_Parameter command to read the CO
2
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 CO2 command. The slave sends the requested CO
2
result and an ACK signal to the master.
1403-116
Figure 14 Get_Parameter with ACK
Wait
Response
Idle
Valid Invoke
Valid Invoke
Response
NACK
Response
ACK + data
Bad Invoke
Bad Invoke
Response
NACK
Mas
ter
S
lav
e
Get_Parameter,CO2_ID
I2C write
Get_Parameter,CO2_ID,549, ACK
I2C read