Vaisala HMM105 Manuel d'utilisateur télécharger pdf (Page 8)

Technical Reference _________________________________________________________________

6 _________________________________________________________________ M211638EN-A

HMM105 State Machine

The main and initial state of the HMM105 is Idle, and it will change to

WaitResponse state only when a valid invoke is received. In

WaitResponse state HMM105 expects to see an I

C read operation. After

seeing a read operation the HMM105 outputs its response with

ACK/NACK and status signals.

If HMM105 is in WaitResponse state and the master sends a new invoke,

the old response belonging to the old invoke will be lost. When the

master sends the next I

C read command, the HMM105 sends it the

response to the latest invoke.

If HMM105 is in Idle state and I

C read is sent, HMM105 responds with

a NACK-signal. This tells the master that the data which the master may

have received in same I

C read is not valid.

If the HMM105 receives an invalid invoke, it goes to the Idle state. An

invoke message can be invalid because of an unknown command,

erroneous CRC, or invalid message length.

1405-073

Figure 2 HMM105 State Machine

Wait

Response

Idle

Valid Invoke

Response

NACK

Response

ACK + data

Bad Invoke

Response

NACK

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Vaisala HMM105 Manuel d'utilisateur Page 8