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Once the transmitter and receiver modules have been configured, some synchronization must occur before the modules exchange data. Since the receiver accepts data on any clock transition, the receiver core logic must be flushed to properly interpret the start of a new, valid frame. This is especially true when the FSI modules reside on separate devices and are possibly isolated.
The following example provides a suggested approach for establishing a clean communication link on two separate devices that power up in an arbitrary order. Note that this is only a sample synchronization. Depending on application requirements, a different approach can be followed. The single, most important aspect of synchronization is to make sure that the receiver is properly flushed and ready to receive a complete frame without error. How to achieve this is up to the application.
Figure 12-2354 shows the connection of the devices in this example. While there is no true concept of a main device or a remote device node in the FSI protocol, the example uses this nomenclature as a simple way to describe the data flow.
Device 1 is the main node; it is the driver of the initialization sequence. Device 2 is the remote node; it responds to the main device commands. In this example, as well as in a real world use-case, neither the main device nor the remote device knows precisely when the other is ready to receive communication.
Sample sequences for both the main device and remote device are provided in the following subsections.