Zx81 ula schematic. ZX81 ULA replacement - vhdl for xc9500xl.

Zx81 ula schematic 11. Note this mixed up connection system will not work for the ROM. 5mm) between the two cover parts (as suggested in If you look at this schematic (where some errors have been corrected, ignore the French video circuitry) which shows the edge-connector connection points (the X's in square boxes), it may help. It's a master piece of simplicity and ingenuity. The other "USA only" components on the schematic are apparently not required The Spectrum ULA was a custom gate array chip that handled the screen, beeper and paging in alternate ROM chips, such as the Interface 1. The ULA uses open-collector outputs on the data bus, and the data bus is pulled high by 8. Please advise me if someone has more ULA for sinclair Timex 1000 or ZX81. An existing Microdrive case is used to house the vDriveZX (check out the installation ZX81 ULA-in-a-CPLD. pdf A4 Paper 1:1 Scale of the Keyboard Mask The ZX81 ULA is a custom gate array that handles the screen, keyboard input, memory access and tape input/output. Discussion forums for users of the Sinclair 8-bit range of computers - ZX80, ZX81, ZX Spectrum, Z88, clones Not many ZX81 / TS1000 programs / games / applications need more than 16K. It does the same thing as a real ZX81 ULA, but its schematic is much easier to read/understand than the ZX80 schematic + Grant's NMI add-on. Schematic (badly named schematic_xc9536 but really needs a xc9572) xc3sprog tp program Sinclair ZX80 / ZX81 / Z88 Forums. Low power consumption. 52v Resistances are as follows: ULA Pin 15 to +5v: 1. (and the ZX81 with all but the last revision of the ZX81 ULA). 50v Pin the ULA removed and IC15 removed: Pin 15 0. The original schematic is available for the ZX8-CCB. The ULA is no longer manufactured, which will mean taking one from a working ZX81 to get this up and running. the first game I was loading required 16 ram and this is a stock zx81. Follow edited Sep 20, 2017 at 11:34. 1K". 7,354 17 17 silver badges 33 33 bronze badges. I inspected it for corrosion, cracks and dry solder joints, then cleaned it with IPA: I opened up the RF modulator box, and inspected it for mods. Does anyone have an idea what this part is? This is my first PCB-project, and I'm trying Bought a couple ZX81, one of them from France. Jul 29, 2007. El modo en el que el ZX81 codifica la memoria de vídeo es The pin-out for the ULA you have there is my diagram for the ULA from a ZX81, not a ZX Spectrum! The original upload of the ZX81 ULA is here. nes / famicom snes / super famicom game boy ds nintendo 64 game cube. I ordered a ZX81 core board for the RC2014 Z80 platform last week. But in a Lambda, the ULA contains the pixel data for the character set. I bought a ZX81 ULA replacement module from you. The vLA81 is a modern plugin replacement for the ZX81 ULA. Schematic Updated Schematic (some errors corrected), but with French video Sinclair ZX80 / ZX81 / Z88 Forums. 2. Spektre Spektre. This is a ZX81 Issue 1 board with 7805 voltage regulator, NEC D780C-1 CPU, Mostek MK36809N-5 ROM, Alliance AS6C62256-55PCN (modern 32k byte) SRAM and 2C210E ULA (a replacement, not the original ULA). These are new ULA replacements created and manufactured by Charlie Ingley. Regular price $50. So I guess next step is to try and log which combinations are duff and map that to a schematic to figure out the cause. I have a ZX81 that has the ULA, the Z80 and the ROM socketed, so that's handy. The ZX Spectrum +2A, +3, Jon shared a link earlier in the discussion to Andy Rea's Ula of which I have ordered one. Work on the specification for the Sinclair ZX80 / ZX81 / Z88 Forums Discussion forums for users of the Sinclair 8-bit range of computers - ZX80, ZX81, ZX Spectrum, Z88, clones About the ZX80 / ZX81 With the ULA removed and IC14 in place: Pin 15 0. The ULA was the reason the ZX81 was inexpensive yet as powerful as more expensive early home computers. . Discussion forums for users of the Sinclair 8-bit range of computers - ZX80, ZX81, ZX Spectrum, Z88, clones About the ZX80 / ZX81. The vLA82 is a modern plugin replacement for the Spectrum 48K ULA (type 6C001E-7 or earlier). the state of the rows is transferred to ZX81 data bits D0-D4 in parallel with the ULA keyboard port. This 40-pin integrated circuit, a Ferranti "ULA2C184E or This repository contains the schematics of the Sinclair ZX81, drawn from the official schematic found in the manual. VCS (2600) 5200 7800 400 AND 800 XL AND XE RANGE LYNX JAGUAR ST RANGE. A link to my mod (with links to the original article) can be found here. See the pin outs thread here. It’s also an evolution based on the ZX80 and we have the circuit schematic for that. The ULA in the ZX81 did more than implement the functionality of the standard TTL chips in the ZX80. An existing Microdrive case is used to house the vDriveZX (check out the installation Sinclair ZX80 / ZX81 / Z88 Forums. Consider the Jupiter Ace, which has a parts count not all that different from the ZX81 or Does anyone have a schematic or any design/product notes for the UM1233 UHF modulator? It doesn't fix 50/60 Hz, NTSC vs. Discussion forums for users of the Sinclair 8-bit range of computers - ZX80, ZX81, ZX Spectrum, Z88, clones The vDriveZX Delivers hardware emulation for up to eight Microdrives and includes a comprehensive toolkit for managing Microdrive Cartridge images which are stored on SD Card. A0-A7, A14/A15: Address Lines; D0-D7: Data Lines; M1; ROMCS; To start, it's simply a matter of attaching the input wires to the back of the ZX81 circuit board: red wire +5V to ULA pin 40, the black wire 0V to ULA pin 34 and the yellow wire to video In at ULA pin 16. I have the schematic, board files I made a schematic where I placed the PTH equivalents of the needed SMT logic of my ZX81+35 ULA replacement, and did a quick check to see if it would fit on this board, and I'm reasonably hopeful it will. Afterwards I got many comments that for a kit it was too difficult to build due to the use of SMT, which is a "bridge too ULA is a type of customizable chip used in many different devices back in the 1970s and 1980s; SCL is the Sinclair Computer Logic chip, customized on the ULA product line. La referencia a la versión la pone en la cara trasera del integrado. Terry Stewart's (Tezza's) Projects and Articles (Blog) Blog index and site links. Installing the ULA The replacement ula includes circuitry to directly drive the composite video input of your monitor or TV, therefore you are required to In parallel with the design, schematics were refined, PCBs finalised, and samples sent out for testing when they became available. Oct 3 rd, 2007, 9:12am Timex Sinclair 1000 - ZX81 « ULA Replacement Functional ULA replacements for the ZX81, Spectrum and 128K/Toastrack. Dec Hex zx81 Schematic (note 1) zx81 Issue 1 internals (note 2) zx81 Issue 3 internals zx81 ZX81 Memotech keyboard Pin 13 is the /ROMCS signal from the ULA to the on board ROM. 9) a placement diagram (drawing) and a Bill of materials that has data Look for ula. zip" and sometimes schematics): Beocomp ZX81 (a version of the ZX81 sold by B&O in the Netherlands) CZ1500 plus TS1500 ringo CP-200 Prologica_CP200_system_s2 TK83 Not many ZX81 / TS1000 programs / games / applications need more than 16K. So like many a proto-nerd in the early 80's, my first "real" computer was a Sinclair ZX-81. Print view; Sinclair ZX80 / ZX81 / Z88 Forums. Installing the ULA The replacement ula includes circuitry to directly drive the composite video input of your monitor or TV, therefore you are required to make a small modification. The successor of the ZX81 is the ZX Spectrum Sinclair ZX80 / ZX81 / Z88 Forums Discussion forums for users of the Sinclair 8-bit range of computers - ZX80, ZX81, ZX Spectrum, Z88, clones About the ZX80 / ZX81 vLA81 : ZX81 ULA replacement. You only need a 6. Schematics_ZX80_81_Printable. If you can unsolder IC's cleanly, internal RAM expansion is easy to do. No extra address decoding was added, so the RAM was limited to 16K. pdf at main · abaffa/zx81 The Sinclair ZX81 was able to be manufactured at such as low cost largely due to the ULA - the "uncommitted logic array". PDF ZX80/81 Schematics by subject. This is easiest done from the transistor schematic and not directly from the ULA die image, because you can read the transistor schematic and begin to understand how it is connected. Post Reply. Original documents written by third-party manufacturers of Sinclair peripherals. April / May 2007. gif" Alwin Henseler's "ZX81_ULA-in-a-CPLD_v1. The ZX Spectrum Reverse Engineering and Clone Desgin Blog I am meticulously back-annotating the resulting images into a schematic, which in it's native transistor form will measure more than 168 x ZX81 ULA Replacement The ZX81 ULA replacement is a plug in pin compatible clone of the original ZX81 ULA with a bit of an extra boost. 52v Pin 16 0. There is a copy of the issue two schematic here. That means, it can be built with all parts still readily available today. For the output wires you have a choice to make, either integrating a small video jack (3. In the schematic (link below), I finalized the schematic of my ZX81 replacement kit (clone) that (unlike my previous effort) uses only off the shelf pin-through-hole components, and will fit inside a real ZX-81 case, or can be built up as a "new" ZX-81 to be put in an enclosure of your choice. I'm going to look around for a ULA now, worst case scenario is that after buying and fitting the parts the machine doesn't work, but I'll have both a removable CPU and ULA to fit into something else. So, long story short: ground pin 22 of the ULA to enable NTSC video. Other than that, it’s a case of obtaining another ZX81 or TS1000 and using it as a donor machine. Ian of Mutant Caterpillar may still have some, but will only fit them as a repair due to being unable to obtain new ULAs. The ZX81 could also switch to fast mode, where it acted like the ZX80 and could run the code at full speed at the expense The problem with the ZX81 is that the CPU-driven video doesn’t turn out to save that much circuitry. Decided to open this one and it's an Issue 3 with 184E ULA. That means, it can be built with all parts still To start, it's simply a matter of attaching the input wires to the back of the ZX81 circuit board: red wire +5V to ULA pin 40, the black wire 0V to ULA pin 34 and the yellow wire ZX81_Detailed_Schematics - Detailed Schematics used to create the PCBs - Gerber file ZX81_Andy_Rea_ULA_Explained - ZX81 and ULA logic based on explained by Andy Rea Whether you want to just get a faulty ZX81 back up and running, or want to extend the ZX81 with expanded memory and HIRES, the vLA81 can provide what you need. Publication. The ZX-ULA2 is a direct replacement for the standard ULA used in the Sinclair ZX81 home computer. He had a very good business from a Cheap and In the schematic referenced above, this is like adding a capacitor between the emitter and video out with the cap (+) on video out and cap (-) on the emitter. This routes the OSC pin of the ULA to A13 of the RAM, so you can use modern CMOS TR6 is a ZTX313 and is connected to pins 11 and 30 of IC2 (the Z80) and pin 33 of IC1 (the ULA). sellmyretro. v file which is code representing ULA chip by FPGA. process the image yourself (cut/crop) beforehand. many thanks. JP1 and JP2 must be positioned accordingly to the This design is based off the schematics from zigg. Any discussions related to the creation of new hardware or software for the ZX80 or ZX81. Improve this answer. Schematic (badly named schematic_xc9536 but really needs a xc9572) xc3sprog tp program the CPLD, from The ZX81 BASIC ROM was also responsible for character generation. I think the Spectrum was a clever evolution - the ZX80 was all commodity chips, the ZX81 got Sinclair started with ULAs (semi-custom chips) and quite possibly helped Ferranti’s ULA business in the process, and then the Spectrum used a bigger ULA and added low-resolution colour. 00 Regular price. To program the CPLD, please refer to the package. Afterwards I got many comments that for a kit it was too difficult to build due to the use of SMT, which is a "bridge too Building a ZX81 clone today with all new parts using the ZX81+38 PCB, with a stylish printed case and a tactile keyboard. The ZX81 is basicly a ZX80 with a new ROM and an NMI generator to help produce a flicker-free display. 1ª versión: 2C158E. Payment with PayPal GIFT (Friends and Family) exclusively. pdf at master · mahjongg2/ZX81plus38 If you unsolder only the ULA side of R28 / R2 when you got three different reference layouts (24 pins chips ZX81 schematic + 28 pins mod on the ZX81 board + 32 pins SRAM), quadruple check your work ! (27C128 to 27C512). 10 schematic. video timing of the blank lines which is controlled by the horizontal sync pulses generated by the NMI hardware in the ULA. Insignia - still no picture 2. My concern with the ULA soldering was that I only soldered under it, I understand that the pads should go through the holes so this should be fine, but I did wonder if I damaged any during the de-soldering / re-soldering Sinclair ZX81 Video Board. The schematic is now function complete, ready to start component placement: added jumpering for alternative ROM's, and support to emulate Existen tres modelos de ULA, ambas partiendo del prototipo de Ferranti 2C000. Ever wondered about the purpose of TR1 in the ZX81 schematic? TR1 together with some passive parts are connected to the CPU WAIT, NMI and HALT lines and generates WAIT states when a NMI pulse occurs. So it's factory fitted, not a mod. Often each person learning more about it. Of course, the ZX Spectrum brought colors and sounds but even the ZX81 had expansions like Chroma and Zonx. 54v Pin 16 0. pdf at master · mahjongg2/ZX81plus38 Introduction. This doubt was removed by adding the 555-based circuit proposed by that question's answer. Soak tested and load/save tested OK. So you don't have to use the one I designed for the ZX-81+35 (although that one should also work fine). Some people like their schematics to show the real, physical connections - I prefer mine to be more concise as I find it makes The ULA Does More Than Output Video. In most cases the existing socket will be OK (unless, of I decided to create this ULA gallery to give people a look at the timeline of probably the most important part of the ZX Spectrum (and ZX81). Yesterday night I converted a tzx of some 1 breakout game. but it only came out to being 17 seconds long and still no dice. I was able to load and run many ZX-81 programs on my ZX81+35 using a laptop sound output as "cassette recorder" with it. This could include broken wires, faulty 4116 DRAM chips, faults with the internal power circuitry, faulty ULA (depending on which version). 47. It lacked the Sinclair ZX80 / ZX81 / Z88 Forums. Print view; Retrotechie, your ringed schematic is identical to mine, I cross checked your diagram with Grants zx81 slow mode adapter and your circuit is completely equivalent. Sinclair ZX80 / ZX81 / Z88 Forums. Related IP Cores ZX81 ULA-in-a-CPLD. ZX81 ULA Replacement. And the zx81 screen reacted when I played it. As there are virtually no old NOS Ferranti ULA's in existence, I am determined to produce my own. They do not match the Datasheet pinouts of the respective RAM /BUSRQ 25 chips. You want the “5C and 6C ULAs” diagram here. The back of the PCB was pretty clean. Clear blacks and no interference Sinclair ZX81 ZXVid - Composite Video/ULA Fix (self-fit) Figure 6-1: Sinclair ZX81 2C210E ULA The ZX Spectrum ULA Having completed the ZX81, Westwood's experience with television saw him move on to television research and development, leaving the clearly capable Altwasser to head development of the ZX81's successor, the ZX82, as the ZX Spectrum was originally called. This Rudedog designed PCB inspired by a schematic at zigg. 8 products. ZX81 has only 4 chips on its mainboard: CPU, ROM, RAM and ULA - a custom logic chip that incorporated all functions of 74xx logic of ZX80. zip contains all the necessary files to create your own ZX81 ULA PCB (schematics, board and gerber files are included). 55 KiB) Viewed 24186 times. 350mA. They then control the relevant memory chips. Providing the functionality of both the earlier 2C158E/184 ULA (without back porch) and the 2C210E (with back porch), the vLA81 also has a few extras added. My ZX81+35, ZX-81 clone, previously called the ZX14 ZX15, and ZX81+34 (2015 Version) retro homecomputer is a much improved Sinclair ZX81 clone built with the modern materials techniques and components of 2015. “Made In Spain” ZX81 and TS1000 PCBs February 23, 2024; How Did TS 2068 Users Make a Spectrum ROM? September 9, 2023; How To Enjoy an Expanded Timex 2068 July 15, 2023; ZX81 Schematic. vLA81 features: Fits within the same 40 pin DIL socket outline as the original ULA. 2022 by cg. Features the Spectrum became Britain’s prevalent gaming machine. 5 million units were sold. ULA Pin Assignments. Shall use a z80 from my minstrel Zx80 board and have a 27c512 with the zx81, Zx80, Jupiter ace rims. You can add a protecting resistor of about 2k2 in series from output of clock gen to input of ULA to be safe. 00 Sale price $50. - zx81/schema/ZX81_Detailed_Schematics. Results: 1. The ZX81 has a clock oscillator made from a 6. due to a difference in the computer models themselves, but the versions of the Uncommitted Logic Array (hereinafter ULA) chips that could be inside of them. This was a technology pioneered by Ferranti, of which Sinclair was one of the first adopters (incorporating all of the discrete logic of the ZX80, plus a NMI generation circuit into the initial ZX81 2C158E ULA). be/N36iWYcXBAEThe most up-to-date v Sinclair ZX81 Overview. lost count!) zx81's plus 3 TS1000's , some are issue 1 some are issue 3, some have green resist some have red, and some have 5 chips some have 4!! But can't Simple transistor mod for ZX80/ZX81. Tweet: There is a 5V line (right) and the video input from the ULA (middle). Contribute to WellsWang/zx81ula-vhdl development by creating an account on GitHub. Publication Details. And both /ROMCS and /RAMCS pins are outputs. No modification to the ZX81 circuit board should be allowed, and the We then powered the ZX81 from our adjustable power supply which needed a 9V supply. Welcome, Guest. The Minstrel 3 will run pretty much any ZX81 software. Discussion forums for users of the Sinclair 8-bit range of computers - ZX80, ZX81, ZX Spectrum, Z88, clones m1 c l r clr p r p r /iorq + /wr a 0 disabled by zx81 circuit (u5:a) 9 8 ic15:d 74ls05 2d q5 3clk q6 s 4 r 1 ic19:a 74ls74 2d q5 3clk q6 s 4 r 1 ic18:a 74ls74 12d q9 11clk q8 s 1 0 Sinclair ZX80 / ZX81 / Z88 Forums. No modification to the ZX81 circuit board should be allowed, and the only If you want to buy a ULA replacement, there is the vLA81: https://www. Mij latest ZX81 clone without ULA built from discrete pin through hole components - ZX81plus38/ZX81plus38 rev 1. There were some works involving GAL circuits here (schematic missing?), but the schematic and Look for ula. Your best bet is to obtain a vLA81 (see also the link in an earlier post). It was pretty much the ZX80 schematic. Authors . I have an old version of the ZX81, so there was doubt about the absence of the back porch in the video signal. so it is quite slow, hence this is slow mode. My concern with the ULA soldering was that I only soldered under it, I understand that the pads should go through the holes so this should be fine, but I did wonder if I damaged any during the de-soldering / re-soldering But it definitely has 5 chips (the ULA, ROM, Z80, and two R12038 chips - one is in the section marked IC4 on the circuit board). Thanks for all your help so far. Fully refurbished Sinclair ZX81 with a red Issue 3 board and 2C210E ULA marked with 8307 datecode (7th week of 1983). Filter by. So the most common internal RAM upgrade is to use a 32K byte SRAM chip, but configure the modification so that the Z80’s CPU can only see 16K bytes of the new RAM chip. ZX81 ULA replacement - vhdl for xc9500xl. The ZX81 video circuitry is driven directly by the ULA and, like the Spectrum, that signal is fed into a UHF modulator which converts the composite signal into an While there is no easy way to extract radiant heat from the ZX81 case, the overall temperature level inside has vastly subsided. ZX81 schematic how does it compare? Thread starter olley; Start date Feb 20, 2023; olley. There have been horizontal sync disturbing pulses which are This is a ZX81 Issue 1 board with 7805 voltage regulator, NEC D780C-1 CPU, Mostek MK36809N-5 ROM, Alliance AS6C62256-55PCN (modern 32k byte) SRAM and 2C210E ULA (a replacement, not the original ULA). ZX81 Variations ZX81 Chip Pin-outs ZX81 Video Sinclair ZX80 / ZX81 / Z88 Forums. vcs (2600) 5200 7800 400 and 800 xl and xe range lynx jaguar st range. 2K resistors. It also has a Kayde keyboard attached which uses a little bit of power as well. Generally TV's don't care whether they tune into a VHF or UHF channel as long as the frequency band is ZX81+38 a clone of the ZX-81. ZX81 ULA ZX81 ULA. Previous ULA versions (and by extension the ZX80) don’t output a proper back porch signal, and most people say in that case a ZX8-CCB or ZXVid board will be required (see underneath). It will also work with most ZX81 add ons. The first mod being RF to composite video. The successor of the ZX81 is the ZX Spectrum even more As I understand it, the ZX81 video system, which resides in the ULA like all the rest of the machine-specific logic, works by using the CPU as an address generator: during active scan line, it lets the CPU try to fetch an opcode from video memory, grabs the opcode for itself to use as a character cell byte, feeds the CPU a NOP instead, then uses its own 3-bit counter The ULA implementation follows, where possible, the original ULA timmings, as stated in "The ZX Spectrum ULA: how to design a microcomputer", written by Chris Smith and published by ZX Design and Media, ISBN 978-0-9565071-0-5 A schematic for the piggy-back board is also available. Volume: 1 Issue: 1. vLA1 - Sinclair ZX Interface 1 ULA Replacement. The vDriveZX is simply connected to your Interface 1, either with your existing Microdrives or by itself. That could have been generated and ANDed with the back porch signal to generate a proper front and back porch, but in practice, it does not seem to matter. Top. 14 kB - 02/23/2023 at 13:24 Preview: keyboard_mask. When no key is pressed, the ULA outputs are high-impedance, and the data bus remains pulled high. ULA Pin Assignments ULA Operation The ULA takes the 14MHz master clock feed on pin 39 (Q) from the crystal oscillator and divides that by 2 to provide a more stable 7MHz clock for the video pixel clock, then again to provide a 3. Also there is a spare hole going through to the RCA socket (left). The resulting DXF file was then imported into EAGLE and than mapped to an EAGLE schematic, so I get a consistent EAGLE project. Discussion forums for users of the Sinclair 8-bit range of computers - ZX80, ZX81, ZX Spectrum, Z88, clones As I understand it, the ZX81 video system, which resides in the ULA like all the rest of the machine-specific logic, works by using the CPU as an address generator: during active scan line, it lets the CPU try to fetch an opcode from video memory, grabs the opcode for itself to use as a character cell byte, feeds the CPU a NOP instead, then uses its own 3-bit counter You can build a clock generator like in the ZX80 schematic with a 74LS86 or 74HCT86 and feed the output signal directly to pin 35 of ULA (clock-in). 10. From RevSpace. Only the minimal video and keyboard kept the ZX81 from being a true powerhouse of usability. Bodo Wenzel estudió una ULA que presentaba la falta de blanking y realizó un clon idéntico ¡ Con fallo y todo!. zx spectrum zx81 zx80 cambridge z88 timex-sinclairs ql (quantum leap) c64 and c128 vic-20 c16 and plus/4 amiga pcs. I ended up choosing the ZX81 as a good place to start because it is pretty much just a ULA chip with a little bit of support circuitry. Discussion forums for users of the Sinclair 8-bit range of computers - ZX80, ZX81, ZX Spectrum, Z88, clones Sinclair ZX80 / ZX81 / Z88 Forums. ULA Pin Assignments A0-A6, A14-A15 The Sinclair ZX81 was my first computer, I learned how to program (in basic) using this machine in late 80's. Schematic, documentation and software listing for 24 line input/output port that can be used to program 2716, 2732 and 2764 EPROMs. Pages. Share. D2364C ROM the similar named Z80 CPU pins as per the schematic diagram. ZX81 had no moving parts - the keyboard was membrane-based, there was no power switch or advanced outputs. Discussion forums for users of the Sinclair 8-bit range of computers - ZX80, ZX81, ZX Spectrum, Z88, clones While there is no easy way to extract radiant heat from the ZX81 case, the overall temperature level inside has vastly subsided. El modo en el que el ZX81 codifica la memoria de vídeo es ligeramente diferente si tenemos más de 3,25kB de memoria RAM o menos. FWIW: You may consider moving 1 topic down. There are other variants with slightly different board layouts but the general principle of operation is the same. Sort by. It requires a PC keyboard or equivalent rewired using the same matrix as the ZX81 keyboard as shown in the schematic. Contribute to jjmz/ula-vhdl development by creating an account on GitHub. This should only work on ZX81’s equipped with a 2C210E ULA, though I got the same good output with a 2C184E ULA. Hopefully attaching some self adhesive heatsinks to the ULA will help keep this vital part a little cooler in general, prolonging its lifespan. The RF Modulator is different for the US Timex model (and the US ZX81 which they did sell some of), there are a few other differences. 506 kΩ ULA Pin 15 to +12VA: 1. Schematic of the So I guess next step is to try and log which combinations are duff and map that to a schematic to figure out the cause. com/products/v Disassembly of ROM code and other firmware-related articles. The pin out for the ZX81 ULA is (I hope) correct. As the video output from the computer is an Analogue UHF TV signal we had to use an old PCI TV tuner card on a spare PC to view and capture the video of the output from the ZX81. Using the probe in 10X mode I see on the ULA pin 35: Which looks good to me. Sure I'll post a file tonight. Mark, thanks for the reply and the link for the french schematics. The ULA implementation follows, where possible, the original ULA timmings, as stated in "The ZX Spectrum ULA: how to design a microcomputer", written by Chris Smith and published by ZX Design and Media, ISBN 978-0-9565071-0-5 There are implementations with some enhancements such as Timex hicolour support and ULA+ support. Pin 13 is the /ROMCS signal from the ULA to the on board ROM. So, the ZX81_ULA_PCB. For me personally this has become The ULA is supplied in the ZX81 disabled configuration and can be used as an ordinary ULA once the composite video output modification (above) has been completed. 100% compatible. @ simon-zx81 I have an extensive list of ZX-81 clones, will report later with a list. Does away with the infamous RAM Grant Searle's Build your own ZX80 and ZX80 to ZX81 conversion; Andy Rea's ZX81 ULA Replacement (which lead to his later PLD based design) Chris Smith's book - The ZX Spectrum ULA: How to design a microcomputer; 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. 5 MHz ZF filter or crystal. The main change between the ZX80 and the ZX81 was integration of all the logic into a single ULA chip. I have made amendments around line counter ZX SPECTRUM ZX81 ZX80 CAMBRIDGE Z88 TIMEX-SINCLAIRS QL (QUANTUM LEAP) C64 AND C128 VIC-20 C16 AND PLUS/4 AMIGA PCS. Shortly after the ZX81 was launched I figured out how to connect some TTL chips to a ZX80 (with the 8Kbyte ROM of the ZX81) to give it the same slow mode. These two sources of keyboard Recreation of the original ZX81 Issue1 PCB with rounded traces, a slightly altered version also - Bluescreen2001/ZX81-PCB. Schematic. 5 MHz clock circuit is fed directly to the ULA (IC1 - SINCLAIR COMPUTER LOGIC) on pin 35. It was designed to replace most of the discrete logic chips of the ZX80 to reduce the chip count down to 4 (or 5, if 2 x 2114 RAM chips are fitted). Jump to navigation Jump to search. Discussion forums for users of the Sinclair 8-bit range of computers - ZX80, ZX81, ZX Spectrum, Z88, clones The later ZX81 2C210E ULA also had a back porch signal, probably generated in a similar way. The difference is the Spectrum copied the characters' 8 bytes to its screen memory area (the part in the first 16 K of RAM that was read by the ULA to generate the picture), whereas the conversion from the ASCII codes stored in the ZX81 screen buffer to a sequence of bits to be sent to the ULA was performed by the Z80 (apparently by driving the Existen tres modelos de ULA, ambas partiendo del prototipo de Ferranti 2C000. Schematic Part1 : https://youtu. It had 50 calculator-style keys (including a full-size space bar and two shift keys), 64K of RAM and circuitry to improve tape load Sinclair ZX81 Overview. When a key is pressed on the system's keyboard, the ULA pulls *down* the corresponding data line. Mis conclusiones pueden ser leídas en el artículo ZX81 Video Signal. Discussion forums for users of the Sinclair 8-bit range of computers - ZX80, ZX81, ZX Spectrum, Z88, clones The ZX81 is a home computer that was produced by Sinclair Research and manufactured in Dundee, Scotland, by Timex Corporation. For the ZX-81 ROM, this jumper must have its positions 2-3 shorted. As soon as I've got a ULA, power supply and cables, I'll fire it up, see if it goes pop and report back. ZX81_Detailed_Schematics - Detailed Schematics used to create the PCBs - Gerber file; ZX81_Andy_Rea_ULA_Explained - ZX81 and ULA logic based on explained by Andy Rea; ZX81_Complete - Complete Schematic (ZX80 + Slow Circuit = ZX81) based on Sinclairs ZX80 Schematics and Grant Searle project The ZX81 ULA replacement is a plug in pin compatible clone of the original ZX81 ULA with a bit of an extra boost. The ZX81+38 is a clone of the Sinclair ZX81 home computer that replaces the ULA found in the original with standard logic ICs. Status In progress Obviously the GitHub Page also contains the latest schematic (for revision 1. with a digital frontend-port video fix, and improved cassette input circuitry. Fitted with a ZX8-CCB-SYNC - a "digital" video output for Sinclair ZX80 / ZX81 with special sync generator when using FAST mode or LOAD/SAVE. Discussion forums for users of the Sinclair 8-bit range of computers - ZX80, ZX81, ZX Spectrum, Z88, clones About the ZX80 / ZX81 My reason for opening it was to slap a heatsink on the ULA and change the keyboard membrane for a new item due to some wear and the fact that I've got a new ZXPand interface This is the first of a two part post that will start a series on modding the Sinclair ZX81 and the Timex-Sinclair 1000. Discussion forums for users of the Sinclair 8-bit range of computers - ZX80, ZX81, ZX Spectrum, Z88, clones m1 c l r clr p r p r /iorq + /wr a 0 disabled by zx81 circuit (u5:a) 9 8 ic15:d 74ls05 2d q5 3clk q6 s 4 r 1 ic19:a 74ls74 2d q5 3clk q6 s 4 r 1 ic18:a 74ls74 12d q9 11clk q8 s 1 0 The vDriveZX Delivers hardware emulation for up to eight Microdrives and includes a comprehensive toolkit for managing Microdrive Cartridge images which are stored on SD Card. It was hugely successful; more than 1. The RAM chip Data and Address connections match 26 the connections as they are on the ZX81. 5 MHz ceramic filter identified as X1 in the schematic below. (as TK80 but with 2K RAM), TK82-C (ZX81 with 2K RAM and NMI generator on a daughterboard), TK83 (ZX81, 2K RAM, a ULA chip in place of discrete TTL chips on earlier model The Sinclair ZX81 was one of the early machines produced by Sinclair, and was the replacement for the ZX80 in 1981 – technically they were almost identical, but whereas the ZX80 used discrete components the ZX81 used a Ferranti ULA (Uncommitted Logic Array), reducing the chip count from 21 to 4 and substantially reducing materials costs. answered Sep 20, 2017 at 11:26. - abaffa/zx81 The ULA was the reason the ZX81 was inexpensive yet as powerful as more expensive early home computers. The ULA takes some of the Z80 CPU control signals including some address lines and uses these signals to produce these two signals. It was launched in the United Kingdom in March 1981 as the successor to Sinclair's ZX80 and designed to be a low-cost introduction to home computing for the general public. The ULA is a custom chip designed by Sinclair Research Limited and is responsible for control of the functions of the ZX81, including the screen. Its ULA replacement logic is nearly perfect, and now also supports the iconic My family friend created silkscreen cap stickers to apply along with a schematic for wiring an aftermarket keyboard to the Timex Sinclair 1000/zx81. The Timex 1000 came with 2k of ram rather than 1k like the ZX81 came with and outputs to 60hz NTSC video while the UK model does 50hz PAL video output. Maybe check C6 (100pF) and R4 (18k). Project The main ZX81+38 page; This is a forwarding page to the now marked Completed main page. Ipswich Funster No 32 MH RV and PVC Exp 30 years The Spectrum ULA was a custom gate array chip that handled the screen, beeper and paging in alternate ROM chips, such as the Interface 1. Using the circuit diagram I've tested continuity from all pins on ULA, Z80 and The vLA81 is a modern plugin replacement for the ZX81 ULA. The system will work fine, as the CPU can read and write data to the RAM. Sinclair ZX81 - detailed schematics (reverse engineered). a 555, four resistors, four capacitors, two diodes and two transistors. For schematic and circuit diagrams, or similar A few years back I attempted this mod on a Spectrum, based upon an old magazine article I’d stumbled across on the Internet. Usually a transistor is added to amplify the signal coming from the ULA. Tribute site for the Timex Sinclair 1000/1500 and ZX81. It's just RAM chips on the Zeddy that you have to watch out for Mark. vretrodesign. Others have produced prebuilt versions of that schematic or even complete ULA replacements that are guaranteed to include a back porch. It seems the ZX81 ULA must be using open collector drives on the databus, or at least drivers with much The vLA81 is a modern plugin replacement for the ZX81 ULA. The Kradle was a keyboard and enclosure upgrade for the ZX-81 and TS 1000. RAM packs from other manufacturers are typically a bit more reliable, but may still suffer from 4116 DRAM chip faults. It combined the ZX80's video circuitry and an The ZX81+38 is a clone of the Sinclair ZX81 home computer that replaces the ULA found in the original with standard logic ICs. The aim of this project is to build a ZX81 ULA equivalent circuit using discrete components that are readily available. Adobe Portable Document Format - 118. I discovered one likely issue. I bought a nice DK-Tronics keyboard with a Series 1 motherboard and 1984 ULA, Z80 etc soldered directly to the motherboard. Plugin ULA replacement. 5MHz The ZX81 PCB was designed to be flexible so that it could be used in either 625 line 50Hz TV areas (now known as PAL, but as PAL is a colour system and the ZX81 does not generate colour, it technically is not PAL) or 525 line 60Hz NTSC areas. The /IORQ line from the Spectrum CPU supplies both the interface 1 gate array IC1 and the Spectrum ULA, and is an active low signal. 506 kΩ ULA Pin 16 to +5v: 1. Adobe Portable Document Format - 87. - abaffa/zx81 ZX81 schematic circuit diagram here (this has French video output circuitry, but that does not matter when fault finding the digital circuitry). Winter 1982. There have been horizontal sync disturbing pulses which are Project ZX81plus38; Most people I showed my ZX-81 clone (ZX81+35) said they liked it, but with such a tiny board and with so many "difficult" surface mount components, they doubted whether they would be able to build this kit, so I restarted my effort, to try to build a 100% compatible ZX-81 clone that anybody could build, but now with commonly available pin-through-hole parts. I'm in the process of redrawing the schematics and PCB layout of the ZX80 in my CAD program. Many older PC keyboards use single sided PCBs making it easy to isolate and rewire the keys. Discussion forums for users of the Sinclair 8-bit range of computers - ZX80, ZX81, ZX Spectrum, Z88, clones This implementation was exacly the missing piece of hardware I needed for my own ZX81 clone. An upgraded / replacement ULA for the Sinclair ZX81 is now available. Other very popular computers were the Commodore 64 and the Apple II but were far more expensive (ZX81 was ten times cheaper than Apple II Plus). In most cases the existing socket will be OK. Schematic Updated Schematic (some errors corrected), but with French video ¡ La pantalla se veía tan oscura como con la ULA original! Este inesperado problema, me ha llevado a estudiar más a fondo la señal de vídeo de los ZX81. Note that "ULA" is a Ferranti Paul wrote: ↑ Wed Nov 25, 2020 12:20 pm I looked at your schematic. But just a year later the Commodore VIC20 arrived and two years later the Commodore 64 came out, and due to the march of technology those were more A tribute repository for the Sinclair ZX81 homecomputer. The ZX81 ULA does not contain the pixel data for the character set, as in the ZX81, this is contained in the ROM. My board nearly fully populated and even thinking of a new revision board. To make the Sinclair ZX81 usable on modern TVs, the first step is to perform a 'composite mod', this converts the RF (antenna) output of the ZX-81 into a composite signal by bypassing the RF modulator. It is one of those home computers very popular in the '80s and affordable (£49. The ZX Spectrum 16K/48K ULA went through multiple revisions and is either a 5C or 6C series Ferranti ULA. I couldn't find a schematic online, so I reverse engineered the design for various photos of the board. It is one of several ULA replacements I have made for members of the Sinclair computer family including the vLA81 for the ZX81, the vLA128 for the Spectrum 128K (Toastrack) and +2 (Grey case) and the vLA1 for the Sinclair ZX Interface 1. abaffa Posts: 14 Joined: Thu Jan 28, 2021 5:51 am. Is the additional backporch optional for 2C184 ULA? Also you add a 32k RAM, why not 56K? Will it be possible to jumper to 1K, 2K, 16K, 32K? You seem to use ULA /RAMCS which means 16 only. 12 posts 1; 2; Next; abaffa Posts: 14 The schematic and CPLD code I've already downloaded. vLA81 features: Figure 6-1: Sinclair ZX81 2C210E ULA The ZX Spectrum ULA Having completed the ZX81, Westwood's experience with television saw him move on to television research and development, leaving the clearly capable Altwasser to head development of the ZX81's successor, the ZX82, as the ZX Spectrum was originally called. The ZX81 used one, and the Spectrum used a different one; The SCL Chip is designed around a Universal Logic Array (ULA) made by Ferranti. The ZX Spectrum Reverse Engineering and Clone Desgin Blog I am meticulously back-annotating the resulting images into a schematic, which in it's native transistor form will measure more than 168 x “Made In Spain” ZX81 and TS1000 PCBs February 23, 2024; How Did TS 2068 Users Make a Spectrum ROM? September 9, 2023; How To Enjoy an Expanded Timex 2068 July 15, 2023; ZX81 Schematic. Unfortunately, like most of the ZX Spectrum schematics, there are numerous errors and mistakes. > Recapped with quality Vishay brand capacitors This is in my schematic and in real on my board. vLA82 1. Mark. net which have been around for many years and is tried and tested. The heart of the ZX Spectrum series of computers is a custom chip called the ULA (Uncommitted Logic Array). 888 kΩ ULA Pin 15 to 0v: 214 Ω ULA Pin 16 to 0v: 214 Ω Asking for 28GBP for 1 ULA (and 24GBP for each additional unit), including worldwide postage. There were some works involving GAL circuits here (schematic missing?), but the schematic and Googling for "zx81 ram pack schematic" (just the words, without the quotes), Schematic above points to IC9, but I wouldn't rely on that, just trace the connection & verify with an Ohm meter. But check out the schematic: Sinclair ZX80 / ZX81 / Z88 Forums. Because there was no PCB, I decided to make it. The custom ULA (Uncommitted Logic Array), also referred to as the SCL (Sinclair Computer Logic) chip was first introduced with the ZX81. I might have to order a few BC547 and BC548 transistors and other electronic parts. Is there any safe schematics for this ULA available elsewhere ? Top. If you suspect RAM, and have a 16k RAM pack, plugging in the RAM pack disables the on board RAM (although if the on board The Timex Sinclair 1000 is a rebranded Sinclair ZX81. com/offer/details/38492 https://www. The first pulse on the above schematic is marked as the front porch, although it is not used. Re: Ding-Dong my ULA is dead (ZX81) I have two ZX81, one is perfectly working and I am trying to repair the other one. I don't then see a clock signal either going into the Z80A on pin 6 or from the ULA on pin 14 Sinclair ZX80 / ZX81 / Z88 Forums. - abaffa/zx81 The ULA (Uncommitted Logic Array) is a chip which controls most of the interfaces between the Z80 CPU and peripheral functions. The Sinclair ZX81 is my first computer, in 1982 (kit). Date. Unit price / A tribute repository for the Sinclair ZX81 homecomputer. The summer I turned 13 in 1981, I saved up money from parents and grandparents and allowance cash for a coup Sinclair ZX80 / ZX81 / Z88 Forums. Installation: (See pictures for more details) Note: This backporch mod is not required for ZX81’s with a newer ULA or ULA replacement like the VLA81 that already produces a backporch signal. Here i go over the schematic for the video circuit and the code for the raster generator. It also provided the "slow mode" in which the video display was never interrupted. Schematic diagram of the Spectrum +2 power supply circuit board -Spectrum +2 Datasette Wiring Pinouts: Pinouts from the cassette recorder in the But in fact if you don't enable the clock doubling, my ZX81+35 should be a perfectly functional ZX-81 clone. Please Login or Register. Don't want to use the one in my faithful zeddy whose ula has a nice heat sink. ZX81 ULA function implemented in a Xilinx XC9572 CPLD. "zx96mainboard schematic. Or how I build my own zeddy. Mij latest ZX81 clone without ULA built from discrete pin through hole components - ZX81plus38/building and testing the ZX81+38. What is the usage difference between the "ROM Patch" schematic and the "Barebones" schematic The ZX Spectrum ULA die has been images and is being back-annotated into schematics. SQ Syntax Quarterly. 80 kB - 03/11/2022 at 20:29 ZX81 ULA Explained by Andy Rea. The ZX81+35 will be first built and tested in 2016. The heat generated by the ULA is now able to permeate the cool void sans 7805. It only works for static RAM chips. It lacked the Of course the actual refresh address isn’t actually likely to be correct for the pixel fetch so the ULA replaces the low nine bits with a combination of the character code and the three-bit line counter. I expected that the board will arrive my mailbox next week or so. Narrow IC pins for easy plugin ULA replacement. Print view; I don't have the schematic in a file right now but look on any zx81 schematic and locate Tr1, the transistors I've tried are PN2222A and 2N2369A, both give the same results, I have also varied the relavent the Sinclair 2C210E ULA (Earlier models used 2C184, which is pin compatable) Z80; 2114 x2 or a single 4118 RAM 2364 ROM ztx313 x2 NPN transistor Character set and opcode map. Ideal for preserving the original ZX81 ULA. Everyone else, Also, I have the ULAs bearing 184 and 210. It’s in chronological order, Guesser’s Spectrum Schematics page covers the +2A/+2B/+3 family with excellently detailed redrawn schematics. Problem is still in the logic I think: PokeMon wrote:1. By Andy Rea. Cheers (Community Wiki because mcleod_ideafix’s answer was correct despite being deleted) The pixel fetch is a subversion of the refresh cycle; the ZX81 has the necessary analogue electronics in place to create an equivalent of the Spectrum’s floating bus for the low nine address pins so when the ULA drives its nine address pins, it overwrites the low nine bits of the refresh The vLA81 is a modern plugin replacement for the ZX81 ULA. It was fairly straightforward. I couldn't replicate that, so I am sticking with discrete logic chips. The second phase has been to convert each transistor/resistor based schematic into an equivalent logic gate schematic. The only changes at that point were the replacement of the 2532 ROM chip with a 27C64 EPROM, and the two 2114 RAM chips were replaced by a single 62256 chip. It is one of several ULA replacements I have made for members of the Sinclair computer family including the vLA82 for the Spectrum 48K, the vLA128 for the Spectrum 128K (Toastrack) and +2 (Grey case) and the vLA1 for the Sinclair ZX Interface 1. Sony - very very nice picture. gnd vcc /clkcpu) a7 38 37 39 36 40 33 32 34 31 35 28 27 29 26 30 23 22 24 21 25 3 4 2 5 1 8 9 7 10 6 13 14 12 15 11 18 19 17 20 16 /wr /rd /iorq a0 a1 a2 a3 a4 a5 a6 ZX81 Hardare Hacking - Homebrew ZX8-CCB. 1. Transistors Q10 and Q11 control the /IORQ line input to the Spectrum ULA (IC1 pin 33). Print view; Search Advanced search. 41,836. Hardware-wise, a 1:1 drop-in replacement for a ZX81 ULA. Never tried but should work I think. Weight: I don't know about the ZX-81, but the spare hole in the RF modulator is what me and other people use to route a composite video signal on the ZX Spectrum, effectively bypassing the RF circuit. The output of the 6. When /IORQ is asserted from the Spectrum, the Spectrum's own ULA may inhibit the CPU clock for several cycles. No, not the later co-branded Timex Sinclair version, but an actual honest-to-Sir Clive Sinclair. In the mean time you should be able to confirm by ZX81 ULA replacement - vhdl for xc9500xl. 6,677. PAL, or other issues (like missing back porch - see ULA version) for TV's that have problems with ZX81 video signal. You state ULA 2C210E which has a backporch and add a backporch to it. vLA81 installed in an issue one ZX81. What is the usage difference between the "ROM Patch" schematic and the "Barebones" schematic The initial problem described in the previous question was that the ZX81 was showing a white screen. When the ZX81 is running it consumes approx. Note that I designed a PSG (programmable sound generator) for the older SMT version the ZX-81+35. I believe that every hobbyist who would like to learn how to develop their own projects should The Spectrum is similar except the ULA does more stuff (which can also be done with 74 series logic). Discussions about Sinclair ZX80 and ZX81 Hardware it appears that there is a continued interest among many users to bring "dead" machines back to life with replacement ULA's. So, as far as I am aware, all stocks of the original ULA chips are sold out. You cannot do that from the die image. zx81 board schematics Pictures and a narrative showing how to add composite video to the Sinclair ZX81. Ding-Dong my ULA is dead (ZX81) Discussions about Sinclair ZX80 and ZX81 Hardware. Rich Mellor RWAP Software RWAP Adventures I have 6(or 7. Modern Versions Spectrum For Everyone member Dave ‘Steamy’ Briggs has produced some excellent A tribute repository for the Sinclair ZX81 homecomputer. But just a year later the Commodore VIC20 arrived and two years later the Commodore 64 came out, and due to the march of technology those were more ZX81 has only 4 chips on its mainboard: CPU, ROM, RAM and ULA - a custom logic chip that incorporated all functions of 74xx logic of ZX80. 95 in kit). That's my project, the one I mentioned in the comment to my answer. This backporch mod is not required for ZX81’s with a newer ULA or ULA replacement like the VLA81 that already produces a The ZX Spectrum ULA die has been images and is being back-annotated into schematics. Myself, I've not had the on board 1K RAM chip(s) fail. Discussion forums for users of the Sinclair 8-bit range of computers - ZX80, ZX81, ZX Spectrum, Z88, clones About the ZX80 / ZX81 Unfortunately there is a component in the schematics, that I don't know: "RN1 5. #1: That is correct. ZX81 ULA replacement revisited. I have two ZX81’s, an Issue 3 with ULA version ULA2C184E and an Issue 1, which also has a ULA2C184E ULA. png (37. With an unexpanded ZX81, the ULA does the address decoding and controls both /ROMCS and /RAMCS so as to Schematics I made while studying how the ZX80/81 works. A tribute repository for the Sinclair ZX81 homecomputer. atom bbc micro electron. Will also create a specific ZX81+38 Keyboard PCB, fit to be mounted on top of the original ZX-81 case, but with real keys. net will allow you to replace the insides of a ZX-81 RF modulator with a new PCB that will give your ZX-81 a much better, stable picture on modern televisions. 887 kΩ ULA Pin 16 to +12VA: 1. I know this has been done before and I have seen the great job that Grant Searle ULA (Uncommitted Logic [PDF], with a list of components and a few schematics: iNSPECTING AND CLEANING THE BOARD. ZX81’s are often modified to add composite My ZX81+35, ZX-81 clone, previously called the ZX14 ZX15, and ZX81+34 (2015 Version) retro homecomputer is a much improved Sinclair ZX81 clone built with the modern materials techniques and components of 2015. Read the article. On a ZX Spectrum 128, or ZX Spectrum +2 the ULA is the Ferranti 7K010E (later labelled Amstrad 40056) . What's noteworthy is this mod between the board and the modulator input, check the red box on the diagram I made and the pics on Imgur. The vLA81 is a modern There are several steps which I like to take when performing a complete restoration on a ZX81, which include fixing factory or age-related problems, and future-proofing. Unlike the ZX80's ROM, the ZX81 ROM contains a sub-interpreter to handle floating-point arithmetic. ukx vhvric xucmctc jufja vne uuwss ixfebem fpeyqn pmal zuqy