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Logic Analyzer
The HP 1652B/1653B logic analyzer operation is based around a 68000
Theory of
microprocessor
and proprietary
acquisition ICs. Input data is captured by passive
Operation
probing, reshaped, and stored into memory.
Data Acquisition
The data acquisition for the logic analyzer consists of the data acquisition pods,
acquisition ICs, and the interface to the 68000. Th
is through any of the data acquisition pods. There
.e interface to
are five pods
the target system
available on the
HP 1652B (80 channels) and two pods available on the HP 1653B (32 channels).
Each pod contains 16 input data probes and one external clock input for state
mode measurements.
The data probes can be used for state or timing
measurements.
Each pod consists of a probe tip assembly and a 4.5 foot woven cable. A probe tip
assembly includes 17 twelve-inch probes and a common ground return. This is
connected to one end of the cable. The other end of the woven cable terminates at
the rear panel of the logic analyzer. The.woven cable consists of 17 signal lines, 17
signal return lines, 2 chassis grounds, and 2 power supply lines. All are woven
together with polyarmid yarn.
Each probe input has an input impedance of 100k ohms in parallel with
approximately
8 pF. The probes can be grounded in two ways: with a common
pod ground for state measurements, or with a probe tip ground for higher
frequency measurements.
The input signals are attenuated by a factor of 10 in the passive probe. The signals
are applied to a comparator where they are compared against a voltage threshold
to determine if the voltage level is above or below the threshold level. The
comparator then shapes the single-ended signal and outputs it at an ECL level to
the acquisition IC. The input data is then stored at the acquisition IC.
Arming
Control
The two BNCs on the rear panel are used for arming control of the logic analyzer
acquisition ICs. An arm signal may be output from the ICs to the rear panel
EXTERNAL
TRIGGER
OUT (JlO), or input to the ICs from EXTERNAL
TRIGGER
IN (J9).
HP 16528/1653B
Theory of Operation
Service Manual
6A-7
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