Message Interpreter Layer
The Message Interpreter Layer handles the handshake between the GPIB extender and other
devices on the GPIB. At the same time, the layer monitors the activities that occur on the
GPIB, translates them into equivalent local and remote GPIB messages, and sends these
messages to the Packet Translation Layer.
Packet Translation Layer
The Packet Translation Layer converts the messages that it receives to packets and sends them
to the Link Management Layer. It can also receive packets from the Link Management Layer
and convert them back to local or remote GPIB messages.
Link Management Layer
The Link Management Layer receives packets from the Packet Translation Layer. It sends the
packets to the Parallel-to-Serial Conversion Layer and it stores them in a local buffer. If a
transmission error occurs, the Link Management Layer can re-send the packets from this local
buffer. The Link Management Layer also receives packets from the Parallel-to-Serial
Conversion Layer and checks the packets for transmission errors. If the Link Management
Layer does not detect an error, it sends the packets to the Packet Translation Layer. However,
if it detects a transmission error, then it re-transmits the packets.
Parallel-to-Serial Conversion Layer
The Parallel-to-Serial Conversion Layer accepts packets from the Link Management Layer,
converts them into serial data, and sends the data to the Physical Layer. It also extracts serial
bits from the Physical Layer, reconstructs them back into packets, and sends them to the Link
Management Layer.
Physical Layer
The Physical Layer transmits and receives serial data over the fiber-optic link.
GPIB Basics
This section describes the basic concepts of GPIB, including its physical and electrical
characteristics, and configuration requirements.
The ANSI/IEEE Standard 488.1-1987, also known as General Purpose Interface Bus (GPIB),
describes a standard interface for communication between instruments and controllers from
various vendors. It contains information about electrical, mechanical, and functional
specifications. GPIB is a digital, 8-bit parallel communications interface with data transfer
rates of 1 Mbyte/s and higher, using a three-wire handshake. The bus supports one System
Controller, usually a computer, and up to 14 additional instruments. The ANSI/IEEE Standard
488.2-1992 extends IEEE 488.1 by defining a bus communication protocol, a common set of
data codes and formats, and a generic set of common device commands.
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GPIB-140B User Manual