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172 16800 Series Portable Logic Analyzers Service Guide

8 Theory of Operation

Two different MIBs are used in the 16800 Series logic analyzers:

• The MIB in the 2- slot, high-power frame (for 16804A, 16806A,

16821A, 16822A, and 16823A logic analyzers) has two

module bus FPGAs.

• The MIB in the 1- slot, low- power frames (for 16801A,

16802A, and 16803A logic analyzers) has one module bus

FPGA.

Module Bus FPGA(s)

The Xilinx XC3S500E FPGA is the primary bridge between the

CPU and the measurement modules. It effectively performs a

translation from PCI slot to the proprietary module interface

bus.

In the 2- slot, high-power frame, a second module FPGA, Xilinx

XC2VP20, performs the translation from PCI slot to a second,

high- speed module interface bus.

I/O FPGA

The Xilinx XC2V250 FPGA is the center of the instrument I/O

functions. The system interfaces directly to this part in the

same way it talks to the measurement module slot(s), via a

16- bit multiplexed general purpose bus. The FPGA is loaded

from an on board EPROM at power up. The EPROM contents

can be changed (updated) through the system software via a

JTAG port.

A major function of this FPGA component is system correlation;

time alignment of the measurement modules and possible other

modules connected through the Trigger In connector. This is

done with eight 52- bit counters running at 1.6 GHz, allowing

relative time alignment of eight seperate events. A 100 MHz

clock is also selected from two possible sources (internal,

external) and a synchronizing signal is generated for time

alignment.

A second major function of the FPGA is the logical combination

and routing of the module arm and trigger lines: ARM, TRIG,

FLAG. These signals are used by the modules to start and stop

each other in addition to supplying the signals for real- time

correlation.

The other FPGA functions include a system interface to control

the Trigger In and Trigger Out ports, and a serial DAC

programmer.

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Agilent Technologies 8133A Manual de Serviço Página 172