IEEE-1394 & Mil1394 Bus Diagnostics

IEEE-1394-2008 Serial bus technology provides access to a very  limited number of diagnostic registers, which in turn provide useful but limited diagnostic information. Also, this Serial bus technology provides a means to read both locally and remotely standard defined PHY registers, which provides limited non-configurable status/diagnostic information. In addition, this technology can be used to define an optional Serial bus Management MAINT_UTILITY register, but with no register field definition.

In the early days of AS5643 standardization efforts DapTechnology proposed to amend the the preferred solutions to include more advanced bus diagnostic capabilities. As AS5643 networks are supposed to provide high-reliability as well as high-stability the diagnostic capabilities were easily identified to be inadequate by DapTechnology. However, as the available off-the-shelf silicon provided no in-situ functionality the proposed functional enhancements were see as too complicated to implement by the WG.

Even though related WG efforts ceased, DapTechnology continued with related work and research. This work led to prototypes and early functional modules clearly identifying advanced diagnostic capabilities.


The innovation describes a diagnostic module to locally acquire internal node or device information and log that information for both node and network diagnostic reasons.

The right-hand drawings illustrate a simplified IEEE-1394 network having a Control Computer (CC) System Module connected to the remote System Modules, shown as A through H.  The remote Modules are shown individually.  While it is not required, all System Modules in this example include the Sub-Diagnostic Module.  When the aircraft is parked, the Portable Diagnostic Module is connected to one of the System Modules on the aircraft.  In this example, the Portable Diagnostic Module is connected to node H.

In this example, a connection between nodes B and C is faulty. From the time when logging begins to downloading, the Sub-Diagnostic Module in node B has counted and logged, with a time stamp.  27 port errors on port 1 (the port connected to System Module C) and three bus resets were logged. The System Module in node C counted zero port errors and three bus resets. When the Sub-Diagnostic Module in the System Module in node B detects the 10th port error, the port error threshold is exceeded and the Warning Event enable is true causing Sub-Diagnostic Module in node B to generate a Warning Event indicating the port errors. The Warning Event is received by the Sub-Diagnostic Module in the CC System Module and processed.

The cause (causeCode) of the first bus reset, as logged by the Sub-Diagnostic Module in node B, was loss of synchronization on port 1 and initiate bus reset.  The Sub-Diagnostic Module in node C sees a physical disconnect on port 0 and initiated a bus reset. All other Sub-Diagnostic Modules  in the other System Modules connected to the 1394 bus detected a bus reset but didn’t initiate one. The second bus reset occurred 550 msec after the first bus reset. The Sub-Diagnostic Module in node B reports a cause of connection on port 1 and initiated bus reset while the Sub-Diagnostic Modules in the other System Modules connected to the 1394 bus detect a bus reset, but didn’t initiate one. The third bus reset was initiated by the CC System Module while all other System Modules on the bus detected a bus reset, but didn’t initiate one.

Based on the time synchronized information retrieved from each of the Sub-Diagnostic Module’s logs, using the diagnostic protocol, the Portable Diagnostic Module is able to determine that twisted pair A (TPA) signals connecting port 1 of node B to port 0 of node C is faulty. This information can then be used to provide step by step repair instructions.

A Sub-Diagnostic Module is made up from various functional circuits in a way that it receives signals from the System Module through a Diagnostic Signal interface. This interface passes the signals through to a Diagnostic Signal Evaluation Logic which determines if a signal or combination of signals is an event to be recorded in a Sub-Diagnostic Register and/or the Sub-diagnostic Log Memory. The events recorded in the Register and Log Memory are accessed by the Portable Diagnostic Module or optionally by the Local Host Processor through its interfaces and through the Sub-Diagnostic Protocol Interface. Recorded events placed in the Log Memory are synchronized by a Sub-Diagnostic Synchronization Timer. The Timer receives high resolution time information from a local clock, such as a physical layer clock, and lower resolution network synchronized information from the Sub-Diagnostic Protocol Interface.   

The Sub-Diagnostic Module includes a plurality of registers with generic counters having programmable counter threshold settings and comparators used to test expected and unexpected values. The generic inputs of the registers are connected to various module signals that need monitoring. These signals to be monitored are connected to the Diagnostic Signals interface and the Diagnostic Signal Evaluation Logic.  Also, the registers and the Evaluation Logic are connected to the Log Memory.  The diagnostic signals are then evaluated and either directly logged or registered into the counters for statistics monitoring.



Allows for node specific analysis & event verification, system-wide device and performance analysis as well as custom algorithm for event characterization and notification management

Patent: 1394& AS5643 Diagnostic Module

Title: Diagnostic module for monitoring electronic data transmission

Number:  US9,575,866

Assignee: DapHolding B.V. (parent company of DapTechnology B.V.)

FilingDate:  2014-11-06

GrantDate: 2017-02-21


A Sub-Diagnostic Module that passes signals through to the diagnostic signal evaluation logic where it determines if a signal or combination of signals is an event to be recorded in the sub-diagnostic registers and/or the sub-diagnostic log memory. The events recorded in the registers and log memory are accessed by the Portable Diagnostic Module through the Sub-Diagnostic Module's diagnostic protocol interface. Recorded events placed in log memory are synchronized by the sub-diagnostic time synchronizer.


It is in DapTechnology's core interest to dive forward IEEE-1394 and AS5643 technologies. We invite all interested parties to engage into licensing discussions and ensure a more stable future for the technologies.