National Instruments GPIB-120B User Manual

Also see for GPIB-120B: Manual Installation guide

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National Instruments GPIB-120B User Manual Manual pdf 15 page image

© National Instruments | 2-3GPIB-120B User Manualstill in the FIFO buffer. If this situation is unacceptable for your application, you must useunbuffered mode, in which the 3-wire interlocked behavior of GPIB is maintained.Buffered mode applies only to data transfers. GPIB command bytes are not stored in the FIFObuffers; they are transmitted using the GPIB double-interlocked handshaking protocol.Setting the Data Transfer ModeTo use buffered mode, set the switch to the ON position, as shown in Figure 2-2. To useunbuffered mode, set the switch to the OFF position.Figure 2-2. Switch Setting for Buffered ModeNote The switch to select buffered or unbuffered mode is recessed to avoidunintentional toggling during operation of the GPIB-120B. Flipping the switch mayrequire a flathead screwdriver or similar tool.Verify that the switch on your GPIB isolator/expander is in the desired position before poweringon the unit.Data Direction ControlBus B sends the data lines to Bus A if the Bus B Source Handshake state is true or if a Controlleron Bus A is conducting a parallel poll.Bus A sends the data lines to Bus B if the Bus A Source Handshake state is true or if a Controlleron Bus B is conducting a parallel poll.Parallel Poll DetectionControllers can conduct parallel polls on Bus A or Bus B, and devices on both Bus A and Bus Bcan respond to parallel polls.If a Controller on Bus A conducts a parallel poll, the parallel poll detection circuitry on side Bconducts a parallel poll on Bus B. The parallel poll result is driven on the data lines of Bus A.If a Controller on Bus B conducts a parallel poll, the parallel poll detection circuitry on side Aconducts a parallel poll on Bus A. The parallel poll result is driven on the data lines of Bus B.Refer to the Parallel Poll Operation section in this chapter for important information aboutconducting parallel polls with the GPIB-120B.ON OFFBUFFERED