Editing Acorn A680 Technical Reference Manual

The '''Acorn Technical Publishing System Technical Reference Manual''' is Acorn Computers' hardware reference for the [[Acorn A680]], which Acorn called the Acorn Technical Publishing System. Part number 0474,905, issue B, July 1988. Chris Whytehead scanned it from the manual that came with his A680 and published it in three parts: the text in two PDFs (114 and 164 pages, with a text layer) and the large drawings as separate files.<ref name="chris">Whytehead, Chris. [https://chrisacorns.computinghistory.org.uk/RISCiXComputers.html "RISC iX Computers: A680"], Chris's Acorns, The Centre for Computing History (retrieved 2026-10-01).</ref> The circuit references in the manual apply to the issue 1 main PCB.

== Contents ==

{| class="wikitable styled-table" style="width:70%; text-align:left;"
|+'''Contents (printed pages)'''
! Chapter or appendix !! Pages !! Hosted file
|-
| 1 Product overview; 2 Main PCB system overview || 1 to 8 || Part 1
|-
| 3 Processor and memory (ARM, master and slave MEMC, clocks, memory array, ROM) || 9 to 22 || Part 1
|-
| 4 The hexadecimal display, including the test ROM LED diagnostics || 23 to 24 || Part 1
|-
| 5 The input/output system (IOC, printer port, serial port, floppy controller, clock/RAM) || 25 to 56 || Part 1
|-
| 6 SCSI; 7 Video; 8 Sound; 9 Keyboard and mouse || 57 to 100 || Part 1
|-
| 10 Podules and backplane || 101 to 136 || Part 2
|-
| 11 Laser printer interface podule; 12 Cartridge tape podule || 137 to 158 || Part 2
|-
| 13 Power supply unit || 159 to 162 || Part 2
|-
| 14 to 20 Floppy drive, cartridge tape drive, internal hard disc, monochrome monitor, external storage unit, streaming tape, external hard disc || 163 to 188 || Part 2
|-
| 21 Ethernet podule || 189 to 204 || Part 2
|-
| Appendices A and B, circuit diagrams and assembly drawings || 205 to 230 || Part 2 (reduced); drawings file
|-
| Appendix C, system PCB links and test points || 231, 232 || Part 2
|-
| Appendix D, parts lists: main PCB, Ethernet podule, laser printer podule, streamer tape podule, 4-way backplane || 233 to 256 || Part 2
|-
| Appendices E to I: device data sheet list, connectors, mechanical specification and standards, bibliography, silk-screen diagrams || 257 to 280 || Part 2
|}

== What it settles ==

* The power supply (chapter 13): a 120 W high-frequency switching unit with +5 V (trimmer adjustable, 4.95 to 5.25 V, 2 to 12 A), +12 V (11.3 to 12.7 V, 0.5 to 3 A), −5 V (0 to 0.25 A) and −12 V (0 to 0.5 A); over-voltage protection on +5 V at 5.8 to 7.0 V; 198 to 264 V input, link-selectable for 90 to 135 V; and the pin assignments of its output cable.
* The built-in hexadecimal display (chapter 4) and the meaning of each test ROM code from 0 to F, the means of diagnosing a board that cannot drive the monitor.
* The clock and CMOS RAM supply (chapter 5): a PCF8583 (IC54) backed by a two-cell dry battery, with diodes D7 and D8 and test point TP3 for the battery voltage.
* The memory options (chapter 3): 4 MB with one MEMC or 8 MB with a master and slave MEMC, and the links that go with each (Appendix C).
* The main PCB parts list (Appendix D), including its electrolytic capacitors and fuses, and the mechanical specification (Appendix G).

== What it does not contain ==

* No internal circuit of the power supply, the monitor or the drives; each is described by its specification only.
* In part 2, Appendices A, B and I are reduced scans of some of the drawings, with pages that carry only a heading between them. The full-size drawings are in the separate drawings file.
* The user guide, programmer's reference manual and service manual that it refers to are not online. Chris Whytehead lists all three as wanted.<ref name="chris" />
* The SCSI chapter calls F1 a 1 A fuse, while the main PCB parts list gives F1 as 500 mA.

== Drawings ==

The drawings file ([[:File:Acorn Technical Publishing System (A680) Technical Reference Manual drawings.pdf]]) has, in order: main PCB circuit diagram sheets 1 to 8; the main PCB silk-screen diagram; the main PCB assembly drawing; and the 4-way backplane, Ethernet/Cheapernet podule, laser printer interface podule and streamer tape controller podule.

== Pages that cite this document ==

* [[Acorn A680]]

<pdf width="800" height="500">File:Acorn Technical Publishing System (A680) Technical Reference Manual part 1.pdf</pdf>

Downloads: [[:File:Acorn Technical Publishing System (A680) Technical Reference Manual part 1.pdf|part 1]], [[:File:Acorn Technical Publishing System (A680) Technical Reference Manual part 2.pdf|part 2]], [[:File:Acorn Technical Publishing System (A680) Technical Reference Manual drawings.pdf|drawings]]

== References ==

<references />

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[[Category:Acorn Service Manuals]]
[[Category:Service Manuals]]
[[Category:Acorn Computers]]