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BBC Micro Advanced User Guide

From RetroTechCollection

The Advanced User Guide for the BBC Microcomputer is a reference book by Andrew C. Bray, Adrian C. Dickens and Mark A. Holmes, published in 1983 by the Cambridge Microcomputer Centre, 153–154 East Road, Cambridge (ISBN 0 946827 00 1). The hosted PDF is the remastered edition by dv8 (2017), seventh revision, April 2023: a retypeset text with a text layer, not a scan of the printed book. Its numbered pages keep the original page numbering and run to p. 510.

It is not an Acorn publication. The authors describe the operating system from OS 1.20, and state that the hardware information was verified on an issue 4 main board, with differences on earlier issues noted where possible. Acorn gave permission to reproduce its circuit diagram and keyboard circuit diagram. Acorn's own service document is the BBC Microcomputer Service Manual October 1985.

Contents

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Part Chapters (page)
Introduction Introduction (5); 1 Introduction for those new to machine code (7)
Operating System commands 2 Operating System commands (11)
Assembly language programming 3 The BASIC assembler (21); 4 Machine code arithmetic (31); 5 Addressing modes (35); 6 The assembler mnemonics (41)
Operating System interfaces 7 Operating system calls (101); 8 *FX/OSBYTE calls (109); 9 OSWORD calls (247); 10 Vectors (253); 11 Memory usage (267); 12 Events (287); 13 Interrupts (295); 14 RS423 (309); 15 Paged ROMs (317); 16 Filing systems (333)
Hardware 17 An introduction to the hardware (353); 18 The video circuit (6845) (359); 19 The video ULA (377); 20 The serial interface (385); 21 The paged ROM select register (395); 22 Programming the 6522 VIA (397); 23 The system 6522, including sound and speech (417); 24 The user 6522 (425); 25 Disc and Econet interfaces (427); 26 The analogue-to-digital converter (429); 27 The Tube (433); 28 The 1 MHz bus (437)
Appendices A *FX/OSBYTE call index (449); B Operating system calls summary (455); C Table of key numbers (456); D VDU codes (459); E PLOT number summary (460); F Screen mode layouts (462); G US MOS differences (478); H Disc upgrade (480); I Circuit board links (482); J Keyboard circuit diagram (489)
End matter Bibliography (491); Glossary (493); Index (499)

What it settles

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  • Appendix I (pp. 482–488) lists the main board's 39 link positions (marked S1 to S39 on its board drawing), with each setting, the factory default and notes. Among them: S25 selects 32K RAM (model B) or 16K (model A); S26 normal or inverted video; S27 the 8 MHz (5.25-inch) or 16 MHz (8-inch) disc clock; S28 and S29 the base or 1200 baud rate; S31 CSYNC polarity; S39 monochrome or colour output on the BNC socket.
  • The same appendix records board-issue differences. Links 35 to 38 exist only on issue 4 boards; on issues 1 to 3 their places are taken by resistors R125, R142, R149 and R153. Links 1, 3, 5 and 6 differ between issue 4 and earlier boards in the same way. A board with a resistor where the table shows a link is an earlier issue, not a modified board.
  • Appendix H (pp. 480–481), on fitting the disc interface, says that a switch-mode power supply must be present, "not a linear supply in a black case", lists the ICs to fit, and gives the auxiliary power socket's ratings: +5 V at 1.25 A, +12 V at 1.25 A and −5 V at 75 mA.
  • Section 28.6.1 (p. 446) states that no power may be drawn from the BBC Micro by 1 MHz bus peripherals.
  • Appendix J reprints Acorn's keyboard circuit diagram (Figure J.2) and the keyboard's eight start-up option links.
  • Chapters 18 and 19 document the 6845 CRTC registers and the video ULA. Chapter 22 reproduces diagrams from Rockwell's R6522 data sheet with Rockwell's permission.

What this book does not contain

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  • The main circuit diagram. The text refers to "the full circuit diagram inside the back cover" (p. 353) and the cover blurb lists it, but the hosted remaster has no foldout and the diagram is not in the file. Acorn's circuit diagram is in the BBC Microcomputer Service Manual October 1985. The keyboard diagram in Appendix J is present.
  • A parts list or component values. Designators appear in the link table and the hardware chapters only.
  • Fault-finding procedures.
  • Power supply internals. The only supply information is the switch-mode requirement and auxiliary socket ratings in Appendix H.

Pages that cite this document

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Download: BBC_Micro_Advanced_User_Guide.pdf

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