The IBWRT "*IDN?" Command in IBIC Results in <ERR TIMO CMPL EABO>
Hardware: GPIB>>Plug-in Controllers>>GPIB-1014, GPIB>>Plug-in Controllers>>GPIB-1014
Problem: I have configured my GPIB board and it passes the Diagnostic test. I am following the communication example from the
Interactive Control (IBIC) web page, but I get an <ERR TIMO CMPL EABO> during the ibwrt. The sequence of commands is:
ibfind gpib0
ibsic
ibsre 1
ibdev 0 PAD 0 12 1 0 (PAD is the primary address of your instrument)
ibwrt "*idn?"
Then I get an EABO error.
Solution: TIMO is a timeout error, and EABO indicates that the operation was aborted because of the error. There are several reasons why you might get such an error:
- Problems with DMA
In IBIC, just before the ibdev command, give another command, ibdma 0. This will prevent the GPIB board from using DMA during data transfers. If this works, then your GPIB board is currently unable to use DMA.
If you have a PCI-GPIB board, then make sure that option for PCI Bus Mastering is enabled in your BIOS. See the Related Link on Timeout Errors (EABO) during GPIB Writes on Windows NT 4.0 Systems with PCI-GPIB Boards (below) for more information. If you have an ISA board (such as an AT-GPIB/TNT), then you should either change your DMA channel or disable DMA.
- Wrong Termination Method
Many instruments have a particular termination character they use to signal the end of a message known as an End Of String (EOS) character. The default termination method used by National Instruments GPIB boards is to assert the End Or Identify (EOI) line with the last character sent in a message. Check with your instrument's documentation, to see if it is expecting/using and EOS character instead. If you write a command with the wrong termination character to an instrument, the instrument may ignore your command and the resulting read command will timeout waiting for something on the bus.
- Misunderstood Message
The instrument may not have understood the message you sent it. "*idn?" is a command that only IEEE 488.2 compatible instruments would be expected to know. If you have an older instrument (one that is only IEEE 488.1 compatible), then you should check your instrument's documentation to see which commands the instrument uses.
- Illegal Handshake
GPIB Writes can also result in a timeout. Because of the 3-wire handshaking that goes on when the GPIB controller is writing to another GPIB device, it is possible for the other device to misbehave and fail to complete the handshake according the the 488.1 specification. This could also possibly occur if the handshaking lines in the cable were not connected. Getting a TIMO error is different than getting an ENOL error, however. ENOL indicates that no instrument responded to the listen commands whereas a TIMO usually indicates that the device was successfully addressed to listen but it failed to properly handshake. The best course of action in this case is to try to use an GPIB Analyzer such as the PCI-GPIB+ board to determine where the handshake is going wrong, especially if this is a custom made instrument.
Related Links: Timeout Errors (EABO) During GPIB Writes on Windows NT 4.0 Systems with PCI-GPIB Boards
Attachments:
Report Date: 08/05/1998
Last Updated: 05/07/2004
Document ID: 1C4F71X4
