867B,863
Service Manual
2-24
Digital Circuitry
2-49.
The H8 microprocessor (U25) provides the core of the digital circuitry. The processor
fetches instructions from two 128k x8 ROMs (U11 and U19) in 16-bit words. A single
32k x8 RAM (U20) provides system Read/Write memory. A serial 16k-bit EEPROM
(U23) provides nonvolatile data storage (setup information, calibration constants, and
saved waveforms).
The keypad interfaces directly to the microprocessor through P2; pressing a key
generates an interrupt. The microprocessor determines which key is pressed by setting
the interrupt pin as an output port and reading the port pins connected to the keypad.
The digital gate array (U24) performs the following functions:
•
Decodes addresses to select the device being addressed.
•
Generates clock signals. A 19.2-MHz oscillator is divided down to 9.6 MHz for the
microprocessor, 4.8 MHz for the Fast A/D Converter, 3.84 MHz for the U30 IC, and
6.4 MHz for the LCD controller.
•
Clocks Fast A/D Converter data into high speed RAM (in U24).
•
Detects the minimum and maximum readings over a scan.
•
Uses frequency counters to determine frequency, pulse width, duty cycle, and period.
•
Outputs threshold signals (DAC1 and DAC2). Two pulse-width modulated signals
are output by the DIC and, when RC-filtered, become the DAC1 and DAC2 signals
used for thresholds.
Component Test also uses U24 to generate a sine wave at different frequencies.
Display hardware includes an LCD controller ((U13), a Display RAM (U21, 32k x8),
and an LCD Module, which incorporates row and column drivers. The display controller
and system RAM are on the upper 8 bits of data bus (D8-D15).
RS-232 Serial Port
2-50.
Communications with an external computer or printer is accomplished through an
isolated RS-232 channel. Microprocessor serial port 2 (U25-95 and U25-96) provides an
amplified signal to a photo diode (CR23) for transmission. A photo transistor (Q31) is
used for reception.
Содержание 863
Страница 49: ...Maintenance Disassembly 3 3 5 OFF 1 6 Places 4 5 5 3 3 2 os5f eps Figure 3 1 Disassembly ...
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Страница 52: ...867B 863 Service Manual 3 8 5 1 6 2 3 4 os30f eps Figure 3 2 Reassembly ...
Страница 94: ...List of Replaceable Parts Parts 5 5 15 FLUKE 86X 4001 Sheet 1 of 2 os31_1f eps Figure 5 2 A1 Main PCA ...
Страница 95: ...867B 863 Service Manual 5 16 FLUKE 86X 4001 Sheet 2 of 2 os31_2f eps Figure 5 2 A1 Main PCA cont ...
Страница 96: ...6 1 Chapter 6 Schematic Diagrams Title Page 6 1 A1 Main PCA Assembly 6 3 ...
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Страница 99: ...Schematic Diagrams 6 6 5 FLUKE 867 1001 Sheet 3 of 5 Figure 6 1 A1 Main PCA cont ...
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