It is important to understand that FireAdapter is a “Mil1394 enabling” but not a dedicated and optimized solution for the specific processing of AS5643 type of data transmissions. Usage of OHCI compliant LLC components provides the necessary ability to transmit and receive Asynchronous Stream packets as required by the AS5643 specification for Asynchronous Subscriber Model (ASM) related data traffic.
Furthermore, the Mil1394 compliant versions of FireAdapter provide the specified active transformer coupling essential for support of longer cable length and electrical isolation. These versions also feature hardware supporting multi-bus requirements which is critical for the support of Mil1394 redundancy and fault tolerance.
For a proper system design as well as integration optimization it is important to understand that due to its OCHI compliance FireAdapter will utilize host processor resource for handling all Mil1394 – and specifically ASM - related packet handling tasks. Standard OHCI 1.1 is “Mil1394 unaware” and related functions will have to be implemented in a product-specific application or middleware layer. Such functions include packet encapsulation, data extraction, receive/transmit STOF offsets, etc. As a key example, FireAdapter handles ASM transmission timing entirely in software. The application has full control and responsibility of handling offset relative to the STOF during packet transmission as well as receive offset validations as well as many other verification functions.
While this can be seen as an advantage, implementers have to pay attention to system resource utilization and latency concerns in order to meet the stringent Mil1394 timing requirements. Please also evaluate Dap’s approach to mitigate related challenges and check out FireTrac® and its innovative, resource-saving and industry approved take on embedded and HW assisted support for packet receive/transmit and timing related Mil1394 requirements.