Why can I send command to my machine used MAX sometimes,​but cann't I sometimes?

Question

I'm developing a gpib interface for our machine using your nat9914 ,but when I send a command "*idn?" to my gpib interface used Measure & Automation,sometime communication was interrupt,this interrupt may appear one times when I communicate four times or more times or less times,Mearsure & Automation display "writing" or "Reading" and then display "EABO"

Answer 1

Hi PeiWen,
Are you using our NI-488.2 drivers? If so, which version? EAB0 is a standard GPIB error message:
The EABO error is usually the result of a timeout during a read or a write operation, but it can also be caused by calling the ibstop function, the ibclr function, or similar functions while an I/O operation is in progress. You may receive a timeout during write operations with a PCI-GPIB board, if the PCI bus mastering (an option in the BIOS of your computer) is not enabled. You may receive a timeout during read operations, if the instrument you are reading from did not understand the previous command, so it has nothing to write to you. There are a few reasons why the instrument may not have anything to say:
The message to the instrument may have been misspelled. For example, "*IDN?" is a common identification query for IEEE 488.2 compliant instruments. It is easy to misspell this message as "*IND?", which the instrument will not understand, so it will not generate a message string for you to read from the instrument.
The message to the instrument may contain a command that the instrument does not understand. For example, the "*IDN?" message from the previous example is only understood by IEEE 488.2 compliant instruments. If your instrument is an older, non-IEEE 488.2 compliant device, then it will not understand "*IDN?", so it will not generate a message string for you to read from the instrument.
The instrument may use a particular EOS (end of string) character as its termination method, but you may forget to append this termination character to your message. For example, if your instrument expects a linefeed as the EOS character, then "ID?" will not work, but "ID?\n" (where \n represents a linefeed in IBIC) will.
You may expect to see EOI (end or identify, one of the five bus management lines) as the termination method, but if the instrument does not set the EOI line when it finishes sending its message, any read operation that you perform will time out.
The above information, including explanations of other GPIB errors can be found at: http://digital.ni.com/public.nsf/websearch/2FA525A​8585A92E9862566EE002A3755#EABO
Hope this helps. Thanks for choosing National Instruments.
Anu Saha
Applications Engineering
National Instruments
Anu Saha
Academic Product Marketing Engineer
National Instruments