Click here to navigate to the timexsinclair section, which contains the timexsinclair specific documents. Mastering machine code on your zx spectrum by toni baker chapter 17 disassembling the rom here is the source code for the disassembler from chapter 17 of mastering machine code on your zx spectrum by toni baker as a zasm. This ula was responsible for the zx81s low chip count. The old zx81 rom reset code was designed for 1216k system memories. The complete timex tssinclair zx81 rom disassembly. The timex sinclair and timex sinclair 1500 have full address decoding, so area 819216383 is empty.
One that i was interested in but never had the courage to swap the rom at the time was a rom with a forth operating system on it. Other things like the cheap membrane keyboard used also kept costs down. The zx81s rom was doubled to 8 kb, from the zx80s 4 kb rom. Config zxpand manual config config x config xy press shiftg in k mode replaces llist command the config command is the main method of communicating with and configuring the zxpand interface. Numbers, spaces, and punctuation all end up getting warped a bit as a result. First of all, you will need to open up your zx81 case and remove the top with the zx81 upside down, so that the expansion port is in the top left hand corner, there are two screw holes visible. This enabled a fuller implementation of a version of ansi minimal basic termed sinclair basic by the company. The unexpanded zx80 and zx81 combine a z80 microprocessor, 1kb of static ram, 4 or 8kb of rom and various bits of support logic. Subtract your target row from 24 and put that in register b.
We can assemble, link, and package this program with the following two commands. The sp rom by comprocsys ltd was an addon card for the zx81 that provided 256 x 192 bitmapped graphics, reading and writing of eproms and communication with peripherals through a zilog 8255 pia chip. I have successfully built many if these kits, and have checked all the components, including all the ics, including the ula, which is often faulty, and all work fine. Apart from fast mode, the spec is largely the same, 1k ram, 3. Click here to navigate to the timexsinclair section, which contains the timexsinclair specific documents other peripheral manufacturers. Sinclair zx81 basic programming by steven vickers i. In place of a dedicated monitor, the zx81 was designed to output video to standard television set. Rupert goodwins jonathan g harston marcus lund joe mackay russell marks eduardo yanez parareda adam stonehewer mark street gerard sweeney.
Original documents written by thirdparty manufacturers of sinclair peripherals. The sinclair zx81 also sold by timex as the timex sinclair was a very compact z80 based machine with a membrane keyboard. According to the system variables of the sinclair zx81, memory location 16398 and 16399 form a 16bit value containing the current address of print position in display file. The zx81 s rom was doubled to 8 kb, from the zx80s 4 kb rom. New support commands in an overlay rom for instant availability. Sdmmc card storage with transparent loadsave integration. Trusted for over 23 years, our modern delphi is the preferred choice of object pascal developers for creating cool apps across devices. The original manual has been scanned and is available as a.
Understanding your spectrumbasic and machine code programming dr. This rom only uses the character set when printing to. The machine had no moving parts, not even a power switch, and used a pressuresensitive membrane keyboard for. Rom 8k logic array zxgates zx81 uses only one chip. Using the keyboard in programs has obvious advantages. Minesweeper is written by zxteammember bodo in pure basic. Frank ohara have examined all routines in the rom and. It was launched in the united kingdom in march 1981 as the successor to sinclairs zx80 and designed to be a lowcost introduction to home computing for the general public. With original power supply and fitting instructions sheet. Updates to the zx81 collection zx81 tapes, hardware and. This converts mains electricity into the form that the zx81 uses. The zx81 version of basic is in an 8k rom as opposed to the zx80s 4k.
Consider also, that this 8k rom can be retrofitted to the zx80 instead of. The zx81 a compact, efficient use of technology for the time, the zx81 was a 3. To function correctly sz81 expects to find the zx80. You will also need a television the zx81 can work without one, but you wont be able to see what its doing. Only minor changes have been made to the original source code. Ce amplifier 16, std this is an oldie from 1983 which takes you through the entire design process, and subsequently analyses, the populor commonemitter transistor amplifier.
Designed as a lowcost introduction to home computing, the zx81 was designed to be small, simple, and cheap. Ian logan is widely acknowledged as the leading authority on sinclair computers. Because basic uses some private variables it must reside in. Back door porch this was missing from early zx81 ulas, and resulted in a very dark picture on most modern tvs. In the zx81 the support logic is provided in a single ula. Sinclair zx81 basic programming by steven vickers second. Zxpand manual page 4 of 16 overview the zxpand is an allinone expansion solution for sinclair zx81 computers. This sinclair zx80 computer has been upgraded to the zx81 keyboard but the original rom is still in place. Timexsinclair sold the zx81 in the united states as the ts. To make the machine affordable, the zx81 was designed to use as few components as possible. The speed it offers is likely to make your fluency in machine code develop very strongly.
The complete spectrum rom disassembly primrosebank. Finished pdf to html transcription on 8th october 2009. The other difference is the external case of the zx80 seems to be made of the same stuff they make yoghurt cartons out of, making them very susceptible to damage. As for other first developers, the zx81 already existed at the time, and if memory does not fail me some of the first commercial hits were zx81 adapted titles. The zx80 was very popular straight away, and for some time there was a waiting list of several months for either version of the machine. Minesweeper for your zx81 will also run under zx81 emulator xtender. The tv picture is formed by the external video hardware. All trigonometric stuff is in radians and pi is provided to help you unravel the results. Aug 21, 20 grant searles build your own zx80 and zx80 to zx81 conversion.
In its strictest sense, rom refers only to mask rom the oldest type of solid staterom, which is fabricated with the desired data permanently stored in it, and thus can never be modified. The complete timex ts sinclair zx81 rom disassembly. For basic you need a zx81 with at least 16k ram and the original 8kbasic rom installed. Minesweeper for your zx81 will also run under zx81emulator xtender. The zx81 was an upgrade to the zx80 which had half the rom. Programs were loaded and saved onto audio cassette tape. Mar 23, 2016 mastering machine code on your zx spectrum by toni baker chapter 17 disassembling the rom here is the source code for the disassembler from chapter 17 of mastering machine code on your zx spectrum by toni baker as a zasm. Mar 06, 2017 numbers, spaces, and punctuation all end up getting warped a bit as a result. Send us your 1k zx81, and soon youll receive a rejuvenated machine with 32kb ram, no ram pack wobble, and perfect composite video. Our customers tell us they develop apps 5x faster using our ides. Afterwards i got many comments that for a kit it was too difficult to build due to the use of. For its day, it was incredibly small and densely integrated. The ula chip, described by the zx81 manual as the dogsbody of the system. Yes, this puts 0, 0 just off the lowerright hand side of the screen.
It was designed and built to be inexpensive and, as such, it was a very common first computer for many people. Then the whole 16k ram will be free for your program. It must be a uhf television if its not built to receive bbc2 in the uk then its no good. Another little project on the old zx81 breadboard is.
Clive sinclair recommissioned a company called nine tiles, which had produced the zx80 rom, to develop the new rom software for the zx81. It seemed the fist stage was just to try to build up the zx81 circuit away from a zx81 board, but using the original zx81 chips. Another little project on the old zx81 breadboard is finished and. The sinclair zx81 was released 1981 in the uk and later in 1982 in a slightly modified form as the timex sinclair in the united states. Kybd is a routine which sets up machine control of the keyboard such that only the eight key. Original scanned printouts from 1985 disassembly are available as a series of searchable. For basic you need a zx81 with at least 16k ram and the original 8kbasicrom installed. It was launched in the united kingdom in 1981 as the successor to sinclairs zx80. Now for a brief description of the function of each of the machinecode segments. Otherwise the zx1541 would disable itself, when wants to disable zx81 rom.
Download software for zx81 and emulator here i will present some nice software for your zx81 which is written by zxteam members and cannot be found in other sites. The more of your own stuff you write, the better you will understand the zx81. Grant searles build your own zx80 and zx80 to zx81 conversion. The zx81 is a home computer that was produced by sinclair research and manufactured in. Actually, as far as i remember, there were some oddities in the speccy rom that could only be explained from it being initially a conversion job from the zx81 rom. I also wrote the listing script, which uses the character set data directly from the zx81 rom to produce an authentic zx81 look. Sinclair zx80 updated to zx81 computer computing history.
Understanding your spectrum basic and machine code. The whole of the above most be done in fast mode, or else the save routine will not be executed. In this book, he gives you a complete overview of the way the spectrum operates, both for basic and machine language programming, including numerous demonstration programs. Bring your zx81 up to speed with an internal 32kb ram epansion and a zxvid fitted. If by accident you plug it into the wrong socket in the computer you will do no damage.
The zx81 is a home computer that was produced by sinclair research and manufactured in dundee, scotland, by timex corporation. A machine code editing program, itself written largely in machine code. Expandable 16k ram, incremental 16k ram, klik keyboard, memocalc, memopak centronics interface, memotech keyboard, quick loadsave rom, rompak rom interface. Your children will gain an understanding of computers that will benefit them for. Mastering your timex sinclair personal computer, the zx81 companion us rerelease. Mastering machine code on your zx81 or zx80 by toni baker. An assembly listing of the operating system of the zx81 rom. It could be used in conjunction with the comprocsys aszmic rom or without via zx81 basic commands. Mastering machine code on your zx spectrum by toni baker. The bare unit comes with four wires which need attaching to your zx81. The romcs control is required for sinclair zx81, that has incomplete decoding, so in areas 819216383 and 3276849151 also the buildin rom is seen. Program structure a basic program consists of statements on numbered lines, the line numbering is a requisite, as it is the way a programmer explains to the basic interpreter the basic order in. Tzx files through the computer sound card so that you can load them on to a real zx81. The zx81, released in a slightly modified form in the united states as the timex sinclair, was a home computer produced by sinclair research and manufactured in scotland by timex corporation learn more.
Andy reas zx81 ula replacement which lead to his later pld based design chris smiths book the zx spectrum ula. Emulating the qs chrs board with its original crude manual enable switch is easy. The zx81 was a home computer, released in the united states in a slightly modified form as the timex sinclair, produced by sinclair research and manufactured by the timex corporation. At one stage the new rom for the zx80 and, subsequently, for the zx81 was expected to offer draw, undraw, data, read and restore features. Screenshots were taken using the eightyone emulator. Just as for numbers, you can combine these to make string expressions, like. The zx81 was a lowerchipcount successor to the zx80 a machine i would dearly love to add to my collection. This block is generated when you merge two zx tape files together. The zx81 was never designed to make use of a file system and this should make finding the file you want much easier. Jun 05, 2015 zx81 sp rom disassembly xcode project. Eprom or secondly, use a ram circuit which overlays the rom such as the.
If you have more ram in the adressrange 8k16k or above 32k with m1notcircuit then it can be used for basic. Recoil retro computer image library decodes amiga, amstrad cpc, apple ii, atari 8bit, atari portfolio, ata. Unused sinclair zx81 computer kit, bought many years ago, and never built. Put 8 queens on a chess board i think actually only the last method, in mc works at all. Zx81 full upgrade, mutant caterpillar games ltd retro store. I can remember several adverts for zx81 rom swaps that improved speed. It started with 8k rom and 1k ram on board, the video output was generated by the cpu interleaved with executing basic and machine code programs. However, more modern types such as epromand flash eepromcan be erased and reprogrammed multiple times. The advert promised much faster operation and of course the forth language which tends to suite computers with few resources. Like the zx80, it was a lowcost introduction to home computing for the. However the new code is designed for expanded memory, with ramtop fixed. Mainly of interest to electronics enthusiasts, but sports some interesting features such as selfchanging basic code to simulate. Fitting the zxvid the zxvid can be supplied either fitted within a uhf modulator case, or as a bare unit which you need to fit inside your existing modulator. Z81 a zx81 emulator for vga pcs running linux xz81 a zx81 emulator for x z81txt a textmode zx81 emulator for the linux console.
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