FireLink® & Mil1394 (AS5643)

As the only vendor worldwide, DapTechnology offers a very unique, but extremely powerful addition to its standard 1394b link layer IP core (extended version only). Our active participation in SAE ASD AS-1A3 standards committee together with the close collaboration with many adopters of said standard allows DapTechnology to, not only develop a fully standards compliant extension to the LLC, but also go beyond and/or deviate from the current AS5643 standard.

The Mil1394 package is designed to offload the AS5643 support for the host processor.  The following features are supported in FW:

• AS5643 Protocol timing
  
  • STOF Generation: Accuracy: 200 nsec (for a 12.5 msec frame time)
  • TX Frame Offset Time: 200 nsec (for a 12.5 msec frame time)
  • RX Frame Offset Time Stamps: Accuracy : 200 nsec (for a 12.5 msec frame time)

•  AS5643 Protocol encapsulation
  • Automated STOF/ASM Field Insertion/Extraction (Heartbeat, Vehicle Time, Status Fields)
  • Automated Field Value Updates (Heartbeat, Vehicle Time)
  • Vertical Parity Check Insertion and Verification

• Hardware RX Filter on MessageID and/or Channel

Compared with other implementations using off-the-shelf 1394 LLC silicon (and AS5643 support implemented in SW) this Mil1394 extension to the extended version of the FireLink® drastically improves the overall system performance, offloads host processor and guarantees timing latencies that otherwise can only be accomplished with real-time operating systems.
Please contact DapTechnology if your requirements go beyond the current AS5643 specification. The flexible architecture of the Mil1394 extension allows the integration and support of features/functions that were not considered in the AS5643 standard as they are not supported by standard silicon. Examples could be static LinkIDs (instead the very dynamic nodeIDs), asynchronous stream acknowledgements as well as full System Integrity Management.

The Mil1394 solution takes full advantage of the OHCI-like system architecture of the extended version of the FireLink. From an applications point of view the OHCI-like descriptor block model is perfectly suited for powerful transmission link lists for isochronous stream packets.  Part of the descriptor is a 16 bit timing field which allows for a precise time adjustment for AS5643 transmit offset requirements. Additionally, the descriptor can be run in a looped mode in case a device has to transmit in every STOF frame.

The same mechanism also allows transmitting messages from a single device but utilizing different node specific time slots. Such transmission lists can be perfectly used for simulation projects that may want to simulate an entire network traffic without physically using multiple bus devices.

Additionally, one great benefit of Mil1394 support in the link layer IP Core is the fact that certain fields in the ASM packet structure and/or the STOF packet can be automatically generated/updated. There is no need that a host application should update and create fields like the vertical parity check, certain data fields in the data word or the vehicle time. The LLC can manage the value insertion into the new message automatically.