National Instruments 320682C Limitations on Transfer Size, Multithreading

Chapter 4 GPIB/GPIB-488.2 Library

If you want to use GPIB under Windows 95 and you have an older board, it is recommended that

you upgrade to one of the boards in this list.

Compatibility Driver

The compatibility driver is a 32-to-16-bit thunking DLL that you can use with the Windows 3.1

GPIB driver under Windows 95. All GPIB boards are supported by the compatibility driver. The

compatibility driver has several limitations. In particular, it does not support multithreading and

transfers are limited to 64k bytes.

Windows NT

The GPIB driver for Windows NT is a native 32-bit driver written specifically for Windows NT.

Version 1.0 supports the following boards:

• AT-GPIB

• AT-GPIB/TNT

Version 1.2, due to be released in the second half of 1996, will add support for the PCI-GPIB and

PCMCIA-GPIB.

Limitations on Transfer Size

There are no limitations on transfer size except for the compatibility driver under Windows 95.

The compatibility driver is limited to 64 KB transfers.

Multithreading

If you are using multithreading in an external compiler, you can call GPIB functions from more

than one thread at the same time under Windows NT or under Windows 95 with the native 32-bit

driver. In order to be truly multithreaded safe, you must use on of the following versions of the

GPIB driver.

• For Windows 95: Version 1.1 or later.

• For Windows NT: Version 1.2 or later.

Although previous versions of the drivers support multithreading, they do not support the

ThreadIbsta, ThreadIberr, ThreadIbcnt, or ThreadIbcntl functions. You need

these functions to obtain thread-specific status values when calling GPIB functions from more

than one thread. The global status variables ibsta, iberr, ibcnt, and ibcntl, are not

reliable in this case because they are maintained on a per process basis.