Common Questions

Why can't I use the analyzer to monitor a GPIB application which uses the NI-488.2 ibln or FindLstn command?

You can use the analyzer to monitor an application with these commands, but you cannot select Participate in Acceptor Handshaking in the Settings dialog box of the analyzer. Selecting this feature asserts/unasserts the NDAC and NRFD lines in response to the Talker's assertion/unassertion of DAV in the GPIB handshake sequence. Therefore, when you run an application that executes a FindLstn or ibln command, all possible GPIB addresses are returned.

How does selecting "Participate in Acceptor Handshake" in the Settings dialog box affect the GPIB?

When Participate in Acceptor Handshake is selected, the analyzer circuitry behaves like a GPIB Listener for the duration of the capture and participates in acceptor handshaking on the GPIB. You can use this feature to slow down GPIB transfers to a particular rate and to avoid overflow errors.

How do I choose a handshake rate? What does "Maximum" mean?

You can use the handshake rate to slow down the transfer rate on the GPIB while debugging timing-related problems. Choosing a particular handshake rate guarantees that the transfer rate on the bus will be less than or equal to that rate. Choosing the Maximum rate causes the analyzer to respond as a Listener as fast as it can without causing overflow errors.

How do I define a trigger point to capture a command byte such as TA0?

In the Settings dialog box, set the data lines of the trigger condition by entering either the ASCII or hex equivalent of TA0 or set each of the data lines independently to represent TA0. Set the ATN, DAV, and NDAC lines to 1. Set NRFD to 0. The remainder of the control lines should be set to x. This state of the handshake lines is necessary to guarantee that valid data is present on the data lines.

What do the rows of lights and switches in the Bus Monitor window represent?

The LEDs represent the state of the bus lines at all times. The toggle switches represent the assertion of lines from within the Bus Monitor window of the analyzer. So, if the LED for a particular line is on, and the switch for that line is off (down position), the line is asserted, but not by the Bus Monitor.

What is the difference between active and inactive capture displays?

Active capture displays show GPIB events as they are being captured. In other words, active capture displays are windows into the single capture buffer used to store new GPIB events. Inactive capture displays show previously captured GPIB events statically, so that they are unaffected by newly captured GPIB events. You must make the capture display inactive if you want to use the search or print features.

What do the "Capture Settings" in the Capture Display window mean?

The Capture Settings section of the Capture Display window shows the capture settings that were used when the data in the window was captured. They help you interpret the captured data in the Capture Display window. They are not necessarily the same as the current capture settings.

How do I use the timestamping information in detailed display mode and summarized display mode?

In detailed display mode, where each line can correspond to only one capture event, the timestamp value represents the time elapsed between the event on that line and the previous event. So, if you want to determine the time elapsed between the capture of the first event and the fifth event, add up the timestamp values on the second, third, fourth, and fifth lines.

In summarized display mode, where more than one event can be present on a line, the timestamp value represents the time elapsed between the first event on that line and the first event on the previous line.

How can I prevent overflow errors?

For detailed information about avoiding overflow errors, refer to the Avoid Overflow Errors section.