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Logic Analyzer Concepts
The Analyzer Hardware
GPIB interface
The instrument interfaces to GPIB as defined by IEEE Standard 488.2.
The interface consists of an GPIB controller and two octal drivers/
receivers. The microprocessor routes GPIB data to the controller. The
controller then buffers the 8-bit GPIB data bits and generates the bus
handshaking signals. The data and handshaking signals are then routed
to the GPIB bus through the octal line drivers/receivers. The drivers/
receivers provide data and control signal transfer between the bus and
controller.
RS-232-C interface
The instrument RS-232-C interface is compatible with standard RS-
232-C protocol. The interface consists of a controller and drivers/
receivers. The controller serializes parallel data from the
microprocessor for transmission. At the same time the controller also
receives serial data and converts the data to parallel data characters for
the microprocessor.
The controller contains a baud rate generator that can be programmed
from the logic analyzer front panel. Other RS-232-C communications
parameters can also be programmed from the logic analyzer front
panel.
The drivers/receivers interface the instrument with data
communications equipment. Slew rate control is provided on the ICs
eliminating the need for external capacitors.
Power supply
A low voltage power supply provides all dc voltages needed to operate
the logic analyzer. The power supply also provides the +5 V dc voltage
to the probe cables to power logic analyzer accessories and analysis
probes.
Unfiltered voltages of +12 V, -12 V, +5 V, -5.2 V, and +3.5 V are supplied
to the acquisition board where they are filtered and distributed to the
CPU board, CRT Monitor Assembly, and probe cables.