Configuration and Operation
Chapter 3
GPIB-140 User Manual
3-2
© National Instruments Corp.
OFF
ON
PARALLEL POLL IMMEDIATE
HS488 ENABLE
BUFFERED TRANSFER
= Not used to set data transfer mode
Figure 3-1. Switch Setting for Buffered Data Transfer Mode
HS488 Mode
The GPIB extender has the capability to handle data transfers using the HS488 protocol.
HS488 specifies a means of transferring data among two or more devices using a
noninterlocked handshake protocol. By using HS488, you can transfer data at rates
higher than rates possible using the IEEE 488.1 protocol. For more information on
HS488, refer to Appendix C, Introduction to HS488 .
HS488 Disabled
With HS488 disabled, the GPIB extender sources and accepts data using a three-wire
handshake protocol, even if both the Talker and Listener are able to transfer data using
the HS488 protocol.
HS488 Enabled
When HS488 is enabled, the GPIB extender accepts data using the HS488 protocol after
the Talker indicates that it wants to issue high-speed transfers. When functioning as a
Talker, the GPIB extender always attempts to use the high-speed mode when HS488 is
enabled. FIFO buffers are always used to buffer data during HS488 transfers, even if the
switch that controls the data transfer mode is set to unbuffered mode. While using
HS488 protocol with the GPIB extender, the GPIB cable length should be set to 5 m in
the configuration utility of your IEEE 488.2 driver software for both the local and the
remote system.