ET-3400 Microprocessor Trainer · Volume 7
Reference
This volume collects the ET-3400’s specifications, its parts and part numbers, its memory map and monitor entry points, its model numbers and prices, every manual and document located with the data the project’s hosting rule needs, the related Heath equipment, and further reading. The rest of the dive explains them: the line and dates in volume 1, the circuit in volume 2, the course in volume 4 and programs in volume 5.
7.1 Specifications
As printed in the 1977 manual (595-2021-03, p. 107).
Table 1 — Specifications
| CPU | 8-bit parallel, NMOS, bus-oriented 6800 |
| ROM | NMOS, 1024 bytes |
| RAM | NMOS, 256 bytes (plus sockets for an additional 256 bytes) |
| Clock frequency | 500 kHz (approximately) |
| Display | six 7-segment LED digits |
| Keyboard | hexadecimal (0–F and Reset); 1 through F are dual-function keys that also enter commands |
| Input switches | eight miniature switches in a dual-in-line package (for experiments) |
| LED monitor lights | eight red LEDs with separate input terminals (for experiments) |
| Power supplies | +5 V at 1.5 A (0.5 A available for the breadboard at the output terminal); +12 V and −12 V at 50 mA at the output terminals |
| Power requirements | 105–130 or 210–260 V r.m.s., 50–60 Hz, 30 W maximum |
| Fuse | 3/8 A, slow-blow |
| Dimensions | 12⅛ in wide × 11¾ in deep × 3½ in high (30.8 × 29.8 × 8.9 cm) |
| Net weight | 4 lb (1.8 kg) |
Additional figures from the Theory of Operation and the panel guide: a line-frequency square-wave output and an approximately 1 Hz square-wave output from comparator IC18; φ2 and VMA·φ2 clock outputs; data switches with 4700 Ω pull-ups (closed = logic 0); LED inputs with 8200 Ω pull-downs, driving the LEDs through a 74LS241 and 180 Ω resistors; a Standby position of the power switch that keeps the processor and memory powered (manual, pp. 108–109; Pictorial 8-1).
The ET-3400A, from the catalogues: MC6808 processor, 512 bytes of user-accessible RAM, 1K monitor ROM; +5 V at 1.5 A and ±12 V at 50 mA; 120 V a.c., 50/60 Hz, 30 W; 3½ in high × 12⅛ in wide × 11¾ in deep (Christmas 1982, p. 36; Winter 1991, p. 54).
7.2 Semiconductor complement
Table 2 — Semiconductor complement
| Circuit | Type | Heath part | Function |
|---|---|---|---|
| IC1, IC6, IC7, IC8 | 74LS241 | 443-824 | LED buffer; control and address buffers |
| IC2, IC3, IC20, IC22 | 74LS42 | 443-807 | address and display decoding |
| IC4 | 74126 | 443-717 | tri-state control |
| IC5, IC21 | 74S00 | 443-26 | gating; D0 inversion |
| IC9, IC10 | 74LS243 | 443-839 | data bus transceivers |
| IC11 | MC6800P | 443-827 | microprocessor |
| IC12 | MCM6830A (mask-programmed) | 444-17 | 1K monitor ROM |
| IC13 | 40097 | 443-720 | keyboard buffer |
| IC14–IC17 | 2112-2 | 443-721 | 256 × 4 static RAM (IC16, IC17 with the course) |
| IC18 | LM3302N, LM2901N or µA775 (selected) | 442-616 | line and 1 Hz square waves |
| IC19 | MC6875 | 443-840 | two-phase clock and reset |
| IC23–IC28 | 74LS259 | 443-804 | display latch drivers |
| IC29 | LM78L12 | 442-644 | +12 V regulator |
| IC30 | LM79L12AC | 442-646 | −12 V regulator |
| IC31 | µA309K | 442-30 | +5 V regulator (TO-3) |
| H, I, N, Z, V, C | TIL312 | 411-831 | common-anode seven-segment LED |
| D3–D10 | 1N4149 | — | diodes |
Source: manual, Semiconductor Identification Charts, pp. 110–113. The ET-3400A used an MC6808 (or 6802) with a crystal in place of the MC6800 and MC6875, and two 2114 RAMs on the board an owner described (sebhc list, 2007); its full parts list was not found.
7.3 Memory map and monitor entry points
Table 3 — Memory map and monitor entry points
| Address | Contents |
|---|---|
| 0000–00C4 | user RAM |
| 00C5–00FF | monitor RAM: stacks, breakpoint table, T0/T1 (00EC, 00EE), DIGADD (00F0), USERS (00F2), SWI/IRQ/SWI/NMI vectors (00F4, 00F7, 00FA, 00FD) |
| 0100–01FF | optional user RAM |
| C003, C005, C006 | keyboard columns |
| C110–C16F | display latches (digit 6 = H … 1 = C on A6–A4; segment on A2–A0; D0 = 1 lights) |
| FC00–FFFF | monitor ROM |
Table 4 — Memory map and monitor entry points
| Routine | Address | Routine | Address |
|---|---|---|---|
| RESET | FC00 | OUTSTJ | FD8C |
| MAIN | FC19 | OUTSTO | FD8D |
| OUTSTA | FC86 | ENCODE | FDBB |
| DO | FC8C | INCH | FDF4 |
| RESUME | FC96 | IHB | FE09 |
| REDIS | FCBC | OUTBYT | FE20 |
| BKPT | FCCE | OUTHEX | FE28 |
| MEM | FCF9 | OUTCH | FE3A |
| AUTO | FD0A | OUTST1 | FE50 |
| PROMPT | FD25 | OUTSTR | FE52 |
| DSPLAY | FD7B | STEP | FE62 |
| OPTAB | FF76 | DISTAB | FF96 |
| HEXTAB | FFA6 | CMDTAB | FFB6 |
Source: manual, Memory Map (p. 87) and symbolic reference table (p. 86). Interrupt vectors at FFF8–FFFF point to 00F7 (IRQ), 00F4 (SWI), 00FD (NMI) and FC00 (reset).
7.4 Model numbers
Table 5 — Model numbers
| Number | What it is | Seen |
|---|---|---|
| ET-3400 | Microprocessor Trainer, kit | Christmas 1977 – Winter 1981 |
| ETW-3400 | same, factory assembled | Fall 1978 – Christmas 1981 |
| ETS-3400 | course and trainer ordered together | Christmas 1977 onward |
| ET-3400A / ET-3400-A | revised trainer (6808), kit | Christmas 1981 – 1993–94 |
| ETW-3400A / ETW-3400-A | same, assembled | Winter 1981–82 – 1993–94 |
| ET-3400-AE / ETW-3400-AE | 220 V, 50 Hz versions | Winter 1981–82 – Christmas 1982 |
| ETS-3400A, ETS-3401A, ETS-3400-B | packages of trainer, course and/or accessory | 1980s |
| ETA-3400 | Memory and Input/Output Accessory, kit | Winter 1979 – Christmas 1987 |
| EWA-3400 | same, assembled | Fall 1979 – Fall 1986 |
| ETA-3400-1 | 3K RAM chip set for the accessory | Winter 1979 onward |
| ETS-349 | trainer owners’ system: H9 terminal, ETA-3400, 3K chip set, BASIC | Fall 1979 |
| EE-3401 / EE-3401-A | Microprocessors course | Christmas 1977 onward |
| EE-3401-1, EE-3401-2 | course slides and filmstrip | 1978 onward |
| EB-6401 (EB-6401A) | classroom version of the course | 1978 onward (text © 1978, 1985) |
| EE-3402, EE-3403, EE-3404, EE-3405 | Interfacing, Voice Synthesis, Advanced Microprocessor, Applications courses for the ET-3400A | 1981–1985 onward |
Heath part numbers of note: manual 595-2021; EE-3401 Unit 1 595-2039-02; ETA-3400 software manual 595-2271-01; EB-6401A textbook 595-3429-07; ETA-3400 modification instructions 597-1954-02 (part); final-examination kit 172-5285-3.
7.5 Catalogue appearances and prices
Table 6 — Catalogue appearances and prices
| Catalogue | Page | ET-3400 kit | Wired | ETA-3400 | EE-3401 |
|---|---|---|---|---|---|
| Christmas 1977 (818) | 100 | $189.95 | — | — | $89.95 |
| Winter 1978 | — | $199.95 | — | — | $89.95 |
| Spring 1978 | 97 | $199.95 | — | — | $89.95 |
| Fall 1978 | 88–89 | $189.95 | $240.00 | — | $89.95 |
| Christmas 1978 (842) | — | $189.95 | $240.00 | — | $89.95 |
| Winter 1979 | — | $189.95 | $240.00 | $150.00 | $89.95 |
| Fall 1979 | 68–69 | $209.95 | $280.00 | $160.00 | $89.95 |
| Christmas 1979 | — | $199.95 | $275.00 | $150.00 | $89.95 |
| 1980 (848) | — | $199.95 | $275.00 | $150.00 | — |
| Christmas 1980 | — | $199.95 | $279.00 | $150.00 | — |
| Winter 1981 | — | $224.95 | $299.95 | — | — |
| Christmas 1981 | — | ET-3400A $224.95 | $299.95 | $175.00 | — |
| Winter 1981–82 | 76–77 | ET-3400A $224.95 | $329.95 | $175.00 | $99.95 |
| Christmas 1982 | 36–37 | ET-3400A $229.95 | $329.95 | $175.00 | $99.95 |
| Spring 1984 | — | ET-3400A $239.95 | $339.95 | $175.00 | — |
| Fall 1985 | — | ET-3400A $259.95 | $359.95 | — | — |
| Fall 1986 | — | ET-3400-A $259.95 | $359.95 | $179.95 | — |
| Fall 1987 | 63–64 | ET-3400-A $259.95 | $359.95 | $129.95 | — |
| Christmas 1987 | — | ET-3400-A $259.95 | $359.95 | — | — |
| Winter 1991 (223) | 53–54 | ET-3400-A $279.95 | $399.95 | — | EE-3401-A $99.95 |
A dash in the page column means the page number was not read from the scan; a dash in a price column means no price was found in that issue. Prices were taken from the scans’ text layers and checked against page images for the pages shown in this dive. The EE-3401 price of $89.95 for Winter 1978 to Christmas 1979 is the figure the text layers repeat in each of those issues.
7.6 Manuals and documents
Heath assembly manuals are numbered 595-nnnn with a two-digit printing suffix. The table lists every ET-3400-related document located online, with the data the project’s hosting rule needs. No title below is hosted by this site. Each carries a copyright notice and dates from 1977 or later, so under the project’s rule (host only titles published before 1964 without renewal, or published without a notice before 1 March 1989) none qualifies, and all are link-only. No renewal search was made, because none is needed: works of 1964–1977 were renewed automatically by the Copyright Renewal Act of 1992, and works of 1978 and later need no renewal. None of these titles appears on the Tubular Electronics list of Heath manuals withheld as still in copyright; that list names the ET-3100 and the ETW-3700 among the trainers (Tubular Electronics).
Table 7 — Manuals and documents
| Title | Part no. | Year | Copyright notice seen | Renewal search | Free scan |
|---|---|---|---|---|---|
| Heathkit Manual for the Microprocessor Trainer, Model ET-3400 | 595-2021-03 | 1977 | yes, “Copyright © 1977” on the title page | not needed (see above) | Internet Archive, DLARC (120 pages; no illustration booklet) |
| same, later printing, with Illustration Booklet, schematic, 10/20/80 parts price list and ETA-3400 modification pages | 595-2021-06 | 1977 (printed c. 1980) | yes, © 1977 | not needed | Internet Archive, manuals (159 pages) |
| EE-3401 Microprocessors, Units 1–10 (Unit 1 Number Systems and Codes … Unit 10 Interfacing Experiments), bound with the trainer manual | 595-2039-02 (Unit 1) | 1977 | yes, “Copyright © 1977” in each unit | not needed | Internet Archive (874 pages) |
| Microprocessors, Book 1/Book 2 (classroom text), EB-6401A | 595-3429-07 | 1978, 1985 (10th printing 1988) | yes, “Copyright © 1978, 1985” | not needed | Internet Archive · second scan |
| Software Reference Manual for the Memory and Input/Output Accessory, Model ETA-3400 | 595-2271-01 | 1979 | yes, “Copyright © 1979” | not needed | Internet Archive (99 pages) |
| ETA-3400 schematic | — | about 1979 | not legible on the scan | not needed | Internet Archive |
| ET-3400A assembly manual | not located | about 1981 | — | — | no scan found |
| Introduction to Microprocessors, EC-6800 (course for the ET-6800) | — | 1980 | yes, “Copyright 1980” | not needed | Internet Archive |
Paper reprints of Heath manuals are sold by Data Professionals, now part of the Heath Company (history dive, volume 7).
7.7 Related Heath equipment
Table 8 — Related Heath equipment
| Model | What | Relation |
|---|---|---|
| ET-3200 / A / B | Digital Design Experimenter | the previous trainer in the course sequence; its own dive |
| ET-3100 / A / B | Electronic Design Experimenter (analog) | the first trainer in the sequence; its own dive |
| ETA-3400 / EWA-3400 | Memory and I/O Accessory | memory, cassette, terminal port, FANTOM II monitor, Tiny BASIC |
| H9, H19 | video terminals | used with the ETA-3400 |
| ET-6800 | Microprocessor Trainer, cardboard cabinet, 1981 | beginner’s trainer for the EC-6800 course (Education History, vol. 3) |
| ET-100 | Advanced Microcomputer Trainer, 8088, 1983 | the 16-bit trainer (Education History, vol. 3) |
| ETW-3800 | Microprocessor Trainer with 68HC11 or 8085 modules | the later 8-bit trainer (Education History, vol. 4) |
| HERO 1 (ET-18) | educational robot, 6808 | the same processor family, 1982 |
| H8 | Heath’s first computer, 8080, 1977 | the computer group’s choice of processor; history dive, vol. 5 |
Further reading
- The ET-3400 manual itself, especially its Operation section, sample programs and monitor listing (pp. 45–90): the best introduction to the machine, and a model of how a 1970s monitor program was written and commented. https://archive.org/details/manualsplus_11737
- The original EE-3401 course, all ten units, in one Internet Archive scan. https://archive.org/details/HeathkitET3400MicroprocessorTrainermanualTraining
- Herb Johnson, “Heathkit ET-3400A 6800”, retrotechnology.com: restoration notes on an ET-3400A and an ET-3400, with ROM dumps and links. https://www.retrotechnology.com/restore/et3400A.html
- Scott Baker, “ETA-3400 memory/IO expansion”, smbaker.com, 2020. https://www.smbaker.com/?p=2716
- Lou Frenzel, “The History of Personal Computers, Part 2: The Heathkit Story”, Electronic Design, 2013. https://www.electronicdesign.com/technologies/communications/article/21799215/the-history-of-personal-computers-part-2-the-heathkit-story
- The Heathkit history dive, volume 5 (Heath goes digital), and the Education History, volumes 1–4.
- KIM-1 at Iconic Machines, the other early trainer on which machine code was commonly learned. https://iconic-machines.fubsypoly.com/kim-1/
- World Radio History, Heathkit catalogue archive, the source for every date and price in this dive. https://www.worldradiohistory.com/Archive-Catalogs/Heathkit_Catalogs.htm
Sources
- Heath Company. Heathkit Manual for the Microprocessor Trainer, Model ET-3400, 595-2021-03 and 595-2021-06, © 1977. https://archive.org/details/manualsplus_11737 · https://archive.org/details/HeathkitManualForTheEt-3400MicroprocessorTrainer
- Heath Company. EE-3401 Microprocessors, Units 1–10, © 1977. https://archive.org/details/HeathkitET3400MicroprocessorTrainermanualTraining
- Heathkit Educational Systems. Microprocessors, EB-6401A, © 1978, 1985. https://archive.org/details/6800-Microprocessors-Book-1and-2-Heathkit-1985 · https://archive.org/details/eb-6401-a-heathkit-microprocessors-textbook-10th-ed
- Heath Company. ETA-3400 Software Reference Manual, 595-2271-01, © 1979. https://archive.org/details/manualzilla-id-5640664 ; schematic https://archive.org/details/Heathkit_ETA-3400-Schematic
- Heath Company. Introduction to Microprocessors, EC-6800, © 1980. https://archive.org/details/HeathkitIntroToMicroprocessors1980
- Heathkit catalogues, 1977–1991. World Radio History. https://www.worldradiohistory.com/Archive-Catalogs/Heathkit_Catalogs.htm
- Tubular Electronics, Heathkit manuals and copyright list. https://tubularelectronics.com/?page_id=64
- Southeast Heathkit Computer users’ mailing list, February 2007. https://sebhcmaillist.heathkit.garlanger.com/sebhc/2007-February/002645.html
Comments (0)