Manual

C HAPTER T WO : Control by GPIB
WM-RCM-E Rev D ISSUED: February 2005 21
USE ADDITIONAL DRIVER CALLS
IBLOC is used to execute the IEEE 488.1 standard message Go To Local (GTL); i.e., it returns the
oscilloscope to the local state. The programming example above illustrates its use.
IBCLR executes the IEEE 488.1 standard message Selected Device Clear (SDC).
IBRDF and IBWRTF, respectively, allow data to be read from GPIB to a file, and written from a file to GPIB.
Transferring data directly to or from a storage device does not limit the size of the data block, but may be
slower than transferring to the computer memory.
IBRDI and IBWRTI allow data to be read from GPIB to an integer array, and written from integer array to
GPIB. Since the integer array allows storage of up to 64 kilobytes (in BASIC), IBRDI and IBWRTI should be
used for the transfer of large data blocks to the computer memory, rather than IBRD or IBWRT, which are
limited to 256 bytes by the BASIC string length. Note that IBRDI and IBWRTI only exist for BASIC, since for
more modern programming languages, such as C, the functions called IBRD and IBWRT are far less limited in
data block size.
IBTMO can be used to change the timeout value during program execution. The default value of the GPIB
driver is 10 seconds — for example, if the oscilloscope does not respond to an IBRD call, IBRD will return
with an error after the specified time.
IBTRG executes the IEEE 488.1 standard message Group Execute Trigger (GET), which causes the X-Stream
DSO to arm the trigger system.
National Instruments supplies a number of additional function calls. In particular, it is possible to use the so-
called board level calls, which allow a very detailed control of the GPIB.
NOTE: The SRQ bit is latched until the controller reads the STatus Byte Register (STB). The action
of reading the STB with the command *STB? clears the register contents except the MAV bit (bit 4)
until a new event occurs. Service requesting can be disabled by clearing the SRE register with the
*SRE 0 command.