Chapter 4 Developing Your NI-488.2 Application
© National Instruments Corporation 4-5 NI-488.2 User Manual
Status Word (ibsta)All NI-488.2 calls update a global status word, ibsta, which contains
information about the state of the GPIB and the GPIB hardware. The value
stored in ibsta is the return value of all the traditional NI-488.2 calls,
except ibfind and ibdev. You can examine various status bits in ibsta
and use that information to make decisions about continued processing.
If you check for possible errors after each call using the ibsta ERR bit,
debugging your application is much easier.
ibsta is a 16-bit value. A bit value of one (1) indicates that a certain
condition is in effect. A bit value of zero (0) indicates that the condition
is not in effect. Each bit in ibsta can be set for device-level traditional
NI-488.2 calls (dev), board-level traditional NI-488.2 calls and
multi-device NI-488.2 calls (brd), or all (dev, brd).
Table4-1 shows the condition that each bit position represents, the bit
mnemonics, and the type of calls for which the bit can be set. For a detailed
explanation of each status condition, refer to Appendix B, Status Word
Conditions.
Table 4-1. Status Word Layout
Mnemonic
Bit
Pos
Hex
Valu e Type Description
ERR 15 8000 dev, brd NI-488.2 error
TIMO 14 4000 dev, brd Time limit exceeded
END 13 2000 dev, brd END or EOS detected
SRQI 12 1000 brd SRQ interrupt received
RQS 11 800 dev Device requesting
service
CMPL 8 100 dev, brd I/O completed
LOK 780 brd Lockout State
REM 640 brd Remote State
CIC 520 brd Controller-In-Charge
ATN 410 brd Attention is asserted
TACS 3 8 brd Tal ker
LACS 2 4 brd Listener