Chapter 4
Theory of Operation
© National Instruments Corp.
4-3
GPIB-140 User Manual
Packet Translation Layer
The Packet Translation Layer converts the messages 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 at the same time, 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 Layer and checks the packets for transmission errors.
If no error is detected, the packets are sent to the Packet Translation Layer. If a
transmission error is detected, the Link Management Layer will initiate re-transmission.
Parallel-to-Serial Translation Layer
The Parallel-to-Serial Conversion Layer accepts packets from the Link Management
Layer, converts them into serial data, and sends the data out to the Physical Layer. It also
extracts serial bits from the Physical Layer, reconstructs them back into packets, and
presents them to the Link Management Layer.
Physical Layer
The Physical Layer handles the transmitting and receiving of serial data over the fiber
optic link.
