Keysight E8491B IEEE 1394 PC Link to VXI User Guide 69Using this Chapter IEEE 1394 Fundamentals and Interface OverviewIEEE 1394 Data Transfer ProtocolData transfer over the IEEE 1394 bus can be either asynchronous orisochronous 1. Keysight’s IEEE 1394 based VXI systems use asynchronous datatransfers and a “fair arbitration” protocol to ensure each VXI mainframe has equalaccess to the bus. Figure 4-2 illustrates the concepts of asynchronous datatransfers and fair arbitration.1 Isochronous data transfers broadcast variable amounts of data at regular intervals with noacknowledgement. Isochronous and Asynchronous data transfers can occur on the same bus.Figure 4-2 IEEE 1394 Data Transfer Protocol.VXI mainframe 1 VXI mainframe 3VXI mainframe 2block transferdata packetdata packetdata packetdata packetdata packetdata packetblock transferarbseqdatapacket ack arbseq packetdata ack arbseqdatapacket ackmainframe 1 or 2 mainframe 1 or 2 mainframe 3subaction 1 subaction 2 subaction 3Fairness Interval nsubaction gapsarbitration rest gap arbitration gapF I n-1 n+1F I
