Probes; Comparators; Acquisition Ic - Agilent Technologies 16800 Series Service Manual

Probes

Comparators

Acquisition IC

16800 Series Portable Logic Analyzers Service Guide
Two types of logic acquisition cards can be used: one that
contains 6 probe pods, and one that contains 4 probe pods.
One pod pair is ignored in the 34- channel 16801A and
16821A logic analyzer models.
Each pod is comprised of one cable and contains 16
single- ended data channels, a clock channel, two serial IIC
(Inter- IC, also known as I2C) programming lines for
configuring analysis probes, +5 V for powering analysis
probes, and 22 ground signals. Each cable has a 40- pin
probe cable connector.
The pods provide +5 Vdc ±5% auxiliary power to each 40- pin
probe cable connector. Each connector can deliver up to
300 mA with a maximum of 1.0 A total from the analyzer
card. A current limiting circuit protects the +5 V cable
power from current overload. The VCC_Enable signal is used
to control power to an analysis probe. Currently, the +5 Vdc
is only disabled during the IIC self- test.
A variety of single- ended probes can be connected to the
logic analyzer cables.
The comparators are single- ended devices that interpret
incoming data and clock signals as either high or low. A
threshold voltage provided by a digital- to- analog- converter
(DAC) is coupled to the reference input of the comparator
through a precision resistor. Pod thresholds are individually
adjustable; clock and data share the same threshold. The
comparator outputs drive the acquisition ICs and clock
divider circuitry.
Each Acquisition IC processes 32 channels of data and 2
channels of clock information. The Acquisition ICs perform
data sampling, sequencing, store qualification, pattern
recognition, and counting functions. State or Timing sample
clocks are sent from the Master card to the Acquisition ICs
in each of the Expander cards in a multi- card module.
Sampled data is decelerated and passed to the Memory
Controller for storage in the Acquisition Memory RAM array.
The Acquisition ICs also contain the 4 GHz sample Timing
Zoom circuitry and memory.
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Theory of Operation
185