4
4-1
4
Theory of Operation
4.1
INTRODUCTION
This section describes the theory of operation of the N4865A.
4.2
FUNCTIONAL DESCRIPTION
A block diagram of the N4865A is shown in Figure 4-1. The N4865A is a
microprocessor based device that performs the VXI-11 client functions to
control an Agilent oscilloscope (instrument) from a GPIB bus. The N4865A
also functions as a HTML server for confi guration.
The N4865A is made up of seven major elements, most of which are intercon-
nected to the microprocessor by a common data, address and control signal
bus.
Incoming GPIB commands or device messages are received by the GPIB Inter-
face Chip. Each received command or message interrupts the microprocessor
so it can fetch the message from the GPIB Interface chip. If the decoded mes-
sage is an GPIB device command, it is converted into the equivalent VXI-11
command for the Ethernet Interface chip. Device messages are packetized and
output through the Ethernet Interface chip to the LAN instrument. Response
packets from the LAN instrument are received by the LAN Interface chip and
placed in the GPIB talk buffer. The response data in the GPIB talk buffer is
output on the GPIB bus when the N4865A is addressed to talk.
Other commands like Device Clear and Device Trigger are converted into
their VXI-11 equivalents and sent through the Ethernet interface to the LAN
instrument. A GPIB Serial Poll causes the N4865A to execute a Read Status
Byte on the LAN instrument.
Theory of Operation
Summary of Contents for N4865A
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