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8bit bus monitor

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By: dilshan

This is an AT89S2051 base 8bit bus monitoring utility. This module indicate bus values and notify value changes by a beep. This utility is design to work with any 5V compatible TTL/CMOS - data/address buses.

This device is useful for digital electronic designs and troubleshootings.

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Bill of Materials

Qty Part # Description Schematic ID Source
1 Ec22e9cdd8216d67a6137fb12660f163536299d4 AT89S2051-24PU IC, 8BIT MCU FLASH, 89S2051, DIP20 IC1 Source
1 8cd9e3dacd4e008fbfc4ed3840ea1ed6580add7a M74HC595B1R 8 Bit Shift Register Output Latch (3-State) IC2 Source
1 19bb88824adb0390b52b813db108800468034277 FOXLF036S CRYSTAL, 3.579545MHz, 18PF, THRU HOLE Q1 Source
3 2SC945 2SC945 T1, T2, T3 Source
2 97b934e26673858b1ea5f0123951a273eda44524 HDSP-F101 Low Current Seven Segment displays SSD1, SSD2 Source
1 F50e502f97fc5cecc260b15c040a985f96e426ce MCP320Q Audible Signal SG1 Source
1 95e9631d1373775b33282ca75d5b4a5df7ba0019 CSC09A0110K0GPA RESISTOR, BUS RES N/W, 8, 10KOHM, 2%, SIP RN1 Source
3 903c74b411aa85ebe63892da584f21d327cbde64 PCF14JT22K0 PCF Series Ø 2.3 x 6.5 mm 0.25 W 22 kOhm ±5 % Through Hole Carbon Film Resistor R1, R2, R3 Source
3 F2a1fb2649c25fa577a4aa4236eeb3b4ae4c9208 PCF14JT10K0 RES 10K OHM 1/4W 5% CARBON FILM R11, R12, R13 Source
7 46596fb5a710fb83fb531de3acbc66cac6ebbc1b PCF14JT330R RES 330 OHM 1/4W 5% CARBON FILM R4, R5, R6, R7, R8, R9, R10 Source
2 Ee05b528de310786923388564a9d54b4fdacda58 K150J15C0GF5TL2 Ceramic Multilayer Capacitor C1, C2 Source
1 9d12757d4d6cb844b36e9b30d7789a2943a998be K104K15X7RF5TL2 Ceramic Multilayer Capacitor C3 Source
1 Ff6587fb0759257bbf6f032e416ac2915fd15807 640456-2 HEADER, VERTICAL, 0.1", 2WAY TP1, TP2 Source
1 Aa07c2d8f53e5f80226811d665928a2a44841f95 LPPB501NFFN-RC 50 Position Total Single Row 1.27 mm Pitch Straight Female Header SV1 Source
1 6e3afd221d3edfcfa5ea33b6dc2a83e85643c8d7 1101M2S3CQE2 SLIDE SWITCH, SPDT, ON-ON S1 Source
1 40554044d18bc8cfc8ff57564cbb165ac44b847d 110-99-320-41-001000 DIP Socket IC1 Source
1 6429faafadb1374811471ef5f7e53668daeafa3c 110-99-316-41-001000 DIP Socket IC2 Source
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1. Assembling the circuit

  • To assemble the circuit use the given schematic. It is highly recommended to use appropriate IC sockets for IC1 and IC2.
  • For Q1 (Crystal) use any 3MHz crystal. We test this system with 3.575611MHz and 3.579545MHz crystals.


2. Attach seven segment display (SSD) to IC2

Connections between IC2 and SSD are as follows:

  • IC Pin 1 - Segment G
  • IC Pin 2 - Segment F
  • IC Pin 3 - Segment E
  • IC Pin 4 - Segment D
  • IC Pin 5 - Segment C
  • IC Pin 6 - Segment B
  • IC Pin 7 - Segment A

3. Power Supply

This 8bit bus monitor requires 5V external power supply. In the idle mode this unit draws 15mA of current and in working mode (when inputs get change) this may raise up to 20mA – 30mA. Due to this low power profile, this system can also attach into the PSU of the "testing system".

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1 - Initial project release
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