Buffered Mode
In buffered mode, the GPIB extenders use FIFO (first-in-first-out) buffers to buffer data
between the remote and local units. For long data streams, the data throughput is much higher
than with unbuffered mode.
However, a few applications may not operate properly in buffered mode. For example, a GPIB
device on the local side of the extension is addressed to talk, another device on the remote side
is addressed to listen. When the Talker sources data bytes, the GPIB extenders accept the data
bytes and store them in a FIFO buffer. At the same time, the GPIB extenders read data from
the FIFO buffer and source data bytes to the Listener. If the FIFO buffer contains data, the
number of bytes sourced by the Talker differs from the number of bytes accepted by the
Listener.
GPIB command bytes are not stored in the FIFO buffers; they are transmitted using the GPIB
double-interlocked handshaking protocol.
Setting the Data Transfer Mode
The two GPIB extenders in your extension system must use the same data transfer mode.
To use buffered mode, set the
BUFFERED TRANSFER
DIP switch to the ON position, as
shown in the following figure. To use unbuffered mode, set this switch to the OFF position.
Figure 9. DIP Switch Setting for Buffered Mode
OFF
PARALLEL POLL IMMEDIATE
HS488 ENABLED
BUFFERED TRANSFER
= Not used to set data transfer mode
HS488 Mode
The GPIB extender can handle data transfers using the HS488 protocol. HS488 transfers data
between two or more devices using a noninterlocked handshaking protocol. You can use
HS488 to transfer data at rates higher than rates possible using the IEEE 488 protocol. For
more information about HS488, refer to
on page 21.
Selecting an HS488 Mode
Refer to the following descriptions when selecting the HS488 mode.
HS488 Disabled
If you disable HS488, the GPIB extender sources and accepts data using a three-wire
handshaking protocol, even if both the Talker and Listener can transfer data using the HS488
protocol.
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GPIB-140B User Manual