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Model 2520 Pulsed Laser Diode Test System Service Manual
Troubleshooting
4-11
Digital circuitry
for the following discussion on digital circuitry.
Microcontroller
The core digital circuitry uses a Motorola 68332 microcontroller (U15) running at
16.78MHz. The memory configuration includes a flash EEPROM (U3 and U4) and a
RAM U2 and U17). Flash ROM support allows internal firmware upgrades using either
the serial or GPIB port for downloading new firmware. All calibration constants and the
saved setups are stored in a separate serial EEPROM (U13).
I/O circuits
External communication is provided via GPIB and serial interfaces. A 9914 GPIB
IEEE-488 standard interface IC is used for the GPIB (U5), and an IC (U20) provides the
voltage conversion for the RS-232 port. U35 provides interfacing for the Digital I/O port,
while U46 and Q6-Q11 provide Trigger Link I/O interfacing.
Digital signal processor
U47 is the DSP IC that processes raw voltage and current samples into final readings.
Voltage and current data for the DSP is read from the high-speed FIFO (first-in, first-out)
SRAM circuits (U27, U29, U38-U42, and U49) after being stored there by the A/D
converters.
Display board circuits
The display board includes a microcontroller (U902) that controls the VFD (vacuum fluo-
rescent display) and interprets key data. The microcontroller has four peripheral I/O ports
that are used for the various control and read functions.
The VFD (vacuum fluorescent display) module (DS901) can display up to 49 characters.
Each character is organized as a 5
×
7 matrix of dots or pixels and includes a long under-
bar segment to act as a cursor. The display uses a common multiplexing scheme with each
character refreshed in sequence. Circuitry includes the grid drivers and dot drivers.
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Страница 13: ...1 PerformanceVerification...
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Страница 31: ...2 Calibration...
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Страница 69: ...3 RoutineMaintenance...
Страница 72: ...3 4 Routine Maintenance Model 2520 Pulsed Laser Diode Test System Service Manual...
Страница 73: ...4 Troubleshooting...
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Страница 91: ...5 Disassembly...
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Страница 99: ...6 ReplaceableParts...
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Страница 117: ...A Specifications...
Страница 121: ...B CalibrationReference...
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