GB2078423A

GB2078423A - Microprocessor teaching/ testing apparatus

Info

Publication number: GB2078423A
Application number: GB8020378A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1980-06-20
Filing date: 1980-06-20
Publication date: 1982-01-06

Abstract

Apparatus for teaching/testing the working of a microprocessor consists of a circuit arrangement including an astable multivibrator 4047, a counter 4017, a retriggerable one-shot or monostable multi- vibrator 74123, and manually operable switches S, S<1>, S0, S1 for resetting and single-stepping the microprocessor, in conjunction with a programmer (not shown) for feeding in data, comprised of an arrangement of multiway switches and diodes, together with a set of indicating elements which may be light- emitting diodes or voltmeters, giving a display of the voltage state of any or all address and data pins of the microprocessor. <IMAGE>

Description

SPECIFICATION Microprocessor teaching unit The invention consists of a simple apparatus for teaching the principles of operation of a microprocessor, by practical experience of the pupil, allowing the student to test out the effectiveness of the manufacturer's Instruction Set as decided by the student, and to devise complex programmes, test them practically, and retrieve numerical answers in the binary scale using a 0-5 voltmeter or other indicator of HIGH or LOW. As this is a comparatively new field of teaching, it is not anticipated that any other teaching units of a similar kind are commercially available.

Essentials of the invention are: (1) An arrangement of integrated circuits, including a microprocessor, multivibrator, counter, and retriggerable one shot, toggle switches, microswitches, multiway switches and diodes, giving a single-stepping, resettable microprocessor circuit and simple programmer, with a self-contained, stabilised power supply.

One embodiment of the invention (see Figs.

1 and 2, where Do-D7, earth, and 5v. + of Fig. 1 are assumed to be connected to the corresponding terminals of Fig. 2) employs a Signetics 2650 microprocessor, with a 4047 multivibrator, 401 7 counter, and 741 23 retriggerable one-shot. Two 8-way single pole switches and diodes are used to feed instructions to data pins D2-D7, and a single pole 4way switch with diodes to data pins Do and DI. This arrangement keeps the number of diodes to a minimum using commercially available switches.The power supply employs four 3mm light emitting diodes for a stabilised reference voltage, in conjunction with a By107 2N3055 series-shunt stabiliser Working of this circuit is as follows: When microswitch S is depressed and then released, the 4047 and 401 7. by a method described in patent application no. 8001163 (14 Jan 1980) generate a single pulse which when applied to 9 of the 741 23 produces a squared-up single pulse of approximate duration 0.5 microsecond, and this is applied to the CLOCK input (38) of the 2650 whenever a single clock pulse is required.With toggle switch So open (keeping OPACI < of the 2650 at HIGH), the 2650 is first reset by closing toggle switch S, (giving a series of repeated clock pulses at approximately 15 microsecond intervals), and thereupon depressing and then releasing the RESET microswitch (S').

Toggle switch SI is then opened again ready for single-stepping, and toggle switch So is closed (putting OPACI < to LOW). ready for the first INSTRUCTION. The address pins should then read zero, and the voltmeter 1 connected to OPREQ(24) should read HIGH. The first instruction is fed to the data pins by appropriate setting of the 4-way and two 8-way switches. A single clock pulse is then fed in (by the method described above), and the reading of the OPREQ of the 2650 on voltmeter 1 should then fall to LOW, and the address pins should read 00000001 using voltmeter 2.Subsequent instructions are fed in by resetting the multiway switches, and a number of clock pulses (usually 3 or 6) will be necessary to add 00000001 to the address (ascertainable as a binary number by applying the probe or crocodile clip of voltmeter 2 to the address pins). The content of the 2650 accumulator is ascertainable at any stage by applying the voltmeter 2 probe to the data pins, after applying a WRITE instruction (10110000) followed by 3 clock pulses.

The student can investigate programmes of any degree of elaboration, given sufficient experimental time. A very simple programme illustrating work that can quickly be performed using this device is the following, to investigate the effect of the manufacturer's ROTATE instruction: Address Data Meaning 0 100 LOAD Accumulator 1 10000000 Number loaded 2 01010000 ROTATE Right 3 10110000 WRITE OUTPUT 01000000 4 01010000 ROTATE Right 5 01010000 ROTATE Right 6 10110000 WRITE OUTPUT 00010000 Claims include the following: (1) Diode-cum-multiway switch type programmers (2) The use of LEDs for obtaining a stable reference voltage (3) The particular method (or a slight varation) adopted in Fig. 1 for single-stepping a microprocessor.

(4) Any embodiment of this device using LEDs, or LEDs with transistors, as substitutes for the voltmeters.

(5) Any embodiment not including its own self-contained power supply, or with a slightly different arrangement of switches, or with one or more toggle switches altered to microswitches, or vice versa.

(6) An embodiment with a transistor multivibrator circuit replacing the 4047.

ADDED NOTE Settings 1, 2, 3, 4, 5, 6, 7, 8 of the 8-way switches produce outputs 000, 001, 010, 011, 100, 101, 110, 111 respectively, and 1,2,3, 4 of the 4-way switches 00,01, 10, 11 respectively. The ordered combination of these outputs gives the INSTRUCTION.

Claims

1. A microprocessor teaching unit containing (a) an arrangement of integrated circuits consisting of an astable multivibrator, counter and retriggerable one-shot, with suitable switches, for resetting and then single-stepping a microprocessor, together with (b) a programming device consisting of an arrangement of diodes and multiway switches, for feeding suitahle voltages to the data pins of (c) an incorporated microprocessor, and also (d) an arrangement of voltmeters or of light-emitting diodes with a suitable interface for indicating the voltage state of any number or of all of the address and data terminals of the microprocessor.

2. A microprocessor teaching unit as claimed in claim 1, in which the interface mentioned under (d) consists of a number of transistors and resistors.

3. A microprocessor teaching unit as claimed in claims 1 or 2, in which the method of single-stepping is varied slightly, for example by using a multivibrator and counter followed by a monostable multivibrator, or in which integrated circuits are replaced by equivalent transistor circuits or by a composite integrated device.

4. A microprocessor teaching unit as claimed in claims 1, 2, or 3, with or without a self-contained power supply, or with a slightly different arrangement of switches and/or diodes, or display.

5. A microprocessor teaching or testing unit, as claimed in claims 1, 2, 3, 4, but using a separate microprocessor, not incorporated into the main apparatus, which is to be tested, or demonstrated for teaching purposes.