Synchronisation and trigger distribution across instrumentation networks

Abstract

A system for synchronising the operation of a measurement instrument having a microcontroller, a local oscillator and function circuitry to an external timebase is provided. The system includes a USB Host Controller; an interrupt generator adapted to respond to ITPs by generating respective interrupts and passing the interrupts to the microcontroller; and a timer for measuring an interval between receptions of the ITPs in a time domain of the local oscillator.

1 . An apparatus for transferring trigger signals from a first USB device to a plurality of second USB Devices attached to a USB network with minimal latency, the apparatus comprising:
 communication circuitry adapted for communicating upstream toward a USB Host Controller and communicating downstream toward a plurality of USB devices; and   trigger engine circuitry adapted to observe communication traffic through said apparatus;   wherein said apparatus is adapted to decode upstream directed communication directed to the USB Host Controller from said plurality of USB devices, to search for specific trigger request signals transmitted upstream from said USB network, and to transmit trigger command packets downstream toward said plurality of USB devices upon reception of said trigger request signals, and wherein said trigger command packets are initiated by the apparatus.   
     
     
         2 . An apparatus as claimed in  claim 1 , wherein said trigger engine circuitry is located inline upstream of said circuitry, and is configured to transmit said communication traffic upstream of said circuitry. 
     
     
         3 . An apparatus as claimed in  claim 1 , further comprising multiplexer circuitry adapted to selectively disable an upstream signal connection. 
     
     
         4 . An apparatus as claimed in  claim 1 , wherein
 the communication circuitry comprises USB hub circuitry; and   the trigger engine circuitry is adapted to observe communication traffic upstream of said USB hub circuitry and to transmit communication packets downstream to an upstream port of said USB hub circuitry;   wherein said trigger engine is configured to decode upstream directed communication from a USB network connected downstream of said apparatus, to search for specific trigger request signals transmitted upstream from said USB network, and to transmit trigger command packets downstream toward said USB hub circuitry upon reception of said trigger request signals.   
     
     
         5 . An apparatus as claimed in  claim 4 , configured so that communication from upstream of said apparatus to said USB Hub circuitry passes through said trigger engine circuitry. 
     
     
         6 . An apparatus as claimed in  claim 5 , further comprising multiplexer circuitry adapted to selectively route either an upstream signal path or output of said trigger engine circuitry to said upstream port of said USB hub circuitry. 
     
     
         7 . An apparatus as claimed in  claim 1 , further comprising:
 logic circuitry adapted to compare a plurality of trigger request signals with a predefined Combinatorial Trigger State;   wherein said apparatus is adapted to decode upstream directed communication from said USB devices, to search for specific trigger request signals transmitted upstream from said USB devices, and to transmit trigger command packets downstream toward said USB devices upon reception of said plurality of trigger request signals in correct combinatorial relationship.   
     
     
         8 . An apparatus as claimed in  claim 7 , wherein said combinatorial trigger state includes time dependence. 
     
     
         9 . An apparatus as claimed in  claim 7 , further adapted to:
 open a communication pipe between the a USB Host Controller and said USB devices; and   insert said trigger command into a data packet passing downstream in said communication pipe.   
     
     
         10 . An apparatus as claimed in  claim 7 , further adapted to:
 selectively disconnect said USB devices upstream of a trigger device; and   transmit said trigger command downstream of said trigger engine circuitry.   
     
     
         11 . An apparatus as claimed in  claim 4 , wherein said USB devices include non-SuperSpeed Devices and said trigger command is broadcast by the trigger engine circuitry to said non-SuperSpeed USB devices. 
     
     
         12 . An apparatus as claimed in  claim 4 , wherein said USB devices include SuperSpeed USB Devices and said trigger command is selectively transmitted by a trigger engine circuitry to said SuperSpeed USB devices, each of said SuperSpeed USB devices being addressed using a USB Routing String. 
     
     
         13 . A method of transferring trigger signals from a first USB device to one or more second USB devices attached to a USB network with minimal latency, the method comprising:
 arming said first USB device to receive a Trigger Condition;   said first USB device detecting said Trigger Condition;   said first USB Device responding by transmitting a Trigger Request message upstream to a USB Host Controller of said USB network;   detecting passage of said Trigger Request directed to the USB Host Controller with a Trigger Engine located in said USB network; and   said Trigger Engine responding to detection of said Trigger Request by transmitting a Trigger Command message downstream to said second USB devices, wherein said Trigger Command message is initiated by the Trigger Engine.   
     
     
         14 . A method as claimed in  claim 13 , further comprising:
 opening a communication pipe between a USB Host Controller and said plurality of USB devices; and   inserting said Trigger Command into a data packet passing downstream in said communication pipe.   
     
     
         15 . A method as claimed in  claim 13 , further comprising:
 selectively disconnecting said plurality of USB devices upstream of said Trigger Engine; and   transmitting said Trigger Command downstream of said Trigger Engine.   
     
     
         16 . A method as claimed in  claim 13 , wherein said second USB devices include non-SuperSpeed Devices and said Trigger Command message is broadcast by the Trigger Engine to said non-SuperSpeed Devices. 
     
     
         17 . A method as claimed in  claim 13 , wherein said second USB devices include SuperSpeed USB Devices, wherein said Trigger Engine selectively transmits said Trigger Command to said SuperSpeed USB devices, each of said SuperSpeed USB devices being addressed using a USB Routing String. 
     
     
         18 . A method as claimed in  claim 13 , further comprising:
 arming a plurality of said USB devices to receive respective trigger conditions;   configuring the trigger engine with a specific combinatorial trigger state, said combinatorial trigger state being a combination of trigger states of said USB devices,   said USB devices detecting said respective trigger conditions;   said USB devices transmitting respective trigger request messages upstream to the USB Host Controller of said USB network, said trigger request messages being indicative of respective trigger states of said USB devices;   detecting passage of said trigger requests with said trigger engine;   said trigger engine maintaining a record of a trigger status of each of said USB devices;   said trigger engine comparing said record of trigger status with said combinatorial trigger state;   said trigger engine transmitting a trigger command message downstream to said USB devices upon said trigger status matching said combinatorial trigger state.   
     
     
         19 . A method as claimed in  claim 18 , wherein said combinatorial trigger state includes time dependence, such that temporal relationships between transitions of said respective plurality of trigger states is important.