3-5
Acquisition Control Registers (diagram 5)
The Acquisition Control Registers are the digital control
interface between the System /kP and the switchable
acquisition circuitry. Switching data is written to the
For calibration and diagnostic purposes, the System
Dac is used to send known voltage levels to various cir-
cuits. Those levels may then be adjusted to remove offsets
and set gain levels to achieve analog calibration or to test
the gains and offsets for diagnostic purposes.
System Cac (diagrams 5 and 6)
The System Dac is used in normal operation to set the
various analog control voltages throughout the instrument.
Such things as preamplifier gain, vertical position and
centering, trigger levels, holdoff time, common-mode
adjust, scale illumination, intensity of the various crt
displays, and CCD positions offsets are all controlled by
the System /kP via the System Dac. Digital values
representing the analog voltage levels required for the vari-
ous controls are written to the digital-to-analog converter
(DAC) input registers where they are converted to analog
voltage levels at the inputs to the Sample-and-Hold cir-
cuits. The Sample-and-Hold circuits maintain a fixed out-
put voltage to the controlled circuit between updates by
the System /kP.
All the buttons and knobs located to the right of the crt
(facing the scope) are monitored via circuitry of the Front
Panel. The Auxiliary Front Panel contains the circuitry
required to monitor the bezel buttons (menu selection but-
tons), the push buttons, and the INTENSITY knob (all
located directly beneath the crt). Probe coding for the
vertical-channel and external-trigger BNC connectors and
the 50!"l overload circuits for CH 1 and CH 2 are also
monitored via the Auxiliary Front Panel circuitry.
Front Panel (diagram 4) and Auxiliary Front Panel
(diagram 6)
All the buttons and knobs of the Front Panel and Auxili-
ary Front Panel are "soft" controls and do not directly
activate a circuit function. This fact allows the switch func-
tions and menu labels to be changed (especially the bezel
buttons of the Auxiliary Front Panel which are used to
make menu selections) as necessary. Buttons may be
defined by the System /kPto be push-push on-off, momen-
tary contact, continuous, or toggle switches. Control
changes are monitored by the Front Panel /kP. Potentiome-
ter controls are digitized; and when a change occurs, the
amount and direction of change is sent to the System /kP
to make the appropriate operational changes. Push but-
tons that are pressed are interpreted as to what type of
switch action occurred (from the switch-type definition list)
and that information is sent to the System /kPto make the
appropriate operational changes.
Theory of Operation-2430 Service
Front Panel Processor (diagram 3)
The Front Panel /kP is a special-purpose device used to
respond to switch and control changes. When a control
changes, the Front Panel /kP informs the System /kP so
that the operating state may be altered to match the
requested change. Potentiometer controls are digitized to
provide the necessary change data to the System /kP.The
System /kP notes the control that changed, the amount
and direction of change (if a pot), and sends out the
necessary commands to make the change. New settings
are updated in the nonvolatile RAM so that they will be
available in the event of a power-off. On a power-on, the
Front-Panel /kP receives instructions as to how the
switches are to be interpreted and then begins scanning
the front panel, watching for a control to change. The Sys-
tem /kPis then free to carryon with other functions.
System RAM consists of two memory devices. Tem-
porary storage of data used in carrying out the various
control functions is stored in the volatile System RAM.
Nonvolatile storage of calibration constants and front-
panel settings is provided by a battery-backup system for
maintaining the memory during power-off in the
nonvolatile RAM.
Permanent programming used to control the operation
of the 2430 resides in the System ROM. The System
ROM contains one 16K byte X 8-bit memory device and
four 32K byte X 8-bit memory devices for a total of 144K
bytes of memory. A page-switching scheme is used to per-
mit the System /kP to access all the available memory
addresses of ROM.
System Processor (diagram 1)
The System /kP, under program direction, controls all
the functions of the scope and coordinates the functions of
the two other microprocessors (the Front-Panel /kPand the
Waveform /kP).The System /kP has a 16-bit address bus
and a separate 8-bit data bus. No multiplexing of the data
bus is required. Addresses are decoded to access the
memory-mapped devices on the data bus, and control sig-
nals generated by the System /kP control communication
between the /kP and the bus devices. An extensive inter-
rupt circuit enables devices on the bus to request servicing
when necessary to get new instructions or take other
action. A power-up reset circuit permits an orderly power-
on and power-off sequence of the System /kP.
(horizontal signal versus versus vertical signal), or readout
data. Dynamic offset correction of the vertical and horizon-
tal output amplifiers is provided that minimizes trace shift
due to intensity changes.
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