There are four startup scenarios requiring synchronization between the Host and Module:

1. Simultaneous Host and Module startup, with the Host completing first.
2. Simultaneous Host and Module startup, with the Module completing first.
3. Unilateral hardware/software reset of Module, requiring application reconfiguration.
4. Unilateral hardware/software reset of the Host, requiring re-synchronization of all attribute states and the application Event Cache.

In each case, the Host and Module will perform a Startup Synchronization sequence to synchronize their data and communication states with one another, prior to the Module initiating any automatic network operations. During this phase, the Host is required to configure support for the application endpoints, clusters and attributes.

Upon startup, the Host must issue the Host Startup Ready command. On receiving the Startup Sync Request command from the Module, the Host may enter Startup Synchronization to perform the aforementioned configuration of endpoints, clusters and attributes. The Startup Sync Request command from the Module will include information on which application configurations may be restored from external flash and which the Host must reconfigure. The Host completes the phase by sending the Startup Sync Complete command to the Module.

This page provides illustrated examples of the Startup Synchronization sequence.

Startup Synchronization Sequence

The diagrams in this section illustrate the Startup Synchronization sequence.

The following figure illustrates the sequence when the Module initializes more quickly than the Host (scenario (2)). The Module retries the Startup Sync Request periodically to ensure that the Host receives the message even if the Host starts up slower than the Module.

Upon the Host completing synchronization (by performing all necessary configurations and updates) it will transmit the Startup Sync Complete command to the Module, at which point the Module will initiate the full application, i.e., commence network activities, etc.

Startup Synchronization Request Retries

Note: please note there is an error in the above diagram. The final Startup Sync Complete message should be going from the Host to the Module and not in the direction shown. 

The next figure illustrates the expected Startup Synchronization sequence following the first power up of the Module from its factory default state. In this diagram, the Configuration and Updates phase from the previous figure has been expanded to show key operations performed by the Host.

First Time Startup Configuration Sequence

The next figure illustrates the Startup Synchronization sequence after power up of a configured Module (i.e., subsequent to the state achieved in the previous figure). The application device type does not need to be defined as it is preserved in non-volatile memory. All configured endpoints, clusters and attributes are stored in volatile memory and must be re-configured after any soft or hard reset of the Module.

Subsequent Startup Configuration Sequence

The next figure is a flow chart of how the Host may implement its startup sequence to synchronize with the Module.

Host Startup Configuration Flow Chart