Zx81 ula chip. Plugin ULA replacement.

Zx81 ula chip The ULA, produced by Ferranti for Sinclair, reduced the chip count as required, and brought the retail cost of the machine, in 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. 1) The board predates the original launch date which makes sense and it has hand traced etching. The ULA chip provides many key functions: Synchronising the screen display; The ZX81 was the successor of the ZX80 and was sold in two forms as a kit and assembled version. Understanding how everything works together in a ZX81 is the hard part IMHO. The ROM runs cool. ZXFERD. And it is the ULA that controls the Z80 during the video generation sequence. The other two or three chips run cooler. The main difference between the two versions of the ULAs as far as video output goes The single chip RAM IC4 (+5VDC on pin 24, ground on pin 12) or the two chip RAMs Conversely, the ZX81 has two commands the Spectrum doesn´t: SLOW and FAST. A big thank you to Andy Rea for the ULA replacement module Mark. The custom ULA (Uncommitted Logic Array), also referred to as the SCL (Sinclair Computer Logic) chip was first introduced with the ZX81. Pin 13 feeds the internal series pass voltage regulator that outputs 0. The whole system was completely transparent and compatible with the ZX81 video circuit. ZX81 Chip Pin-outs ZX81 Video Transistor Amp Standby alert There are four lights! Step up to red alert ULA pin 39 on a Sinclair/Ferranti chip is rather sensitive and the capacitance from a ‘scope probe can affect it. Sir, are you absolutely sure? The pin out for the ZX81 ULA is (I hope) correct. Sir, are you absolutely sure? The 2000 series CML ULA (as used for the ZX81 and TS1000) peripheral cells had the following available for the designer to use: 200Ω, 1kΩ, 2kΩ, 3kΩ, 5kΩ and 5kΩ resistors; ZX81 Variations ZX81 Chip Pin-outs ZX81 Video Transistor Amp Standby alert There are four lights! simple video output for ZX81 Could be that the ULA output works like a current source, and needs (a bit more) load to produce correct voltages. You can either use it as a spare, or sell it. Sir, are you absolutely sure? It does mean changing the bulb Are both ULA chips the same, or are they different versions? Mark. In most Got a ZX81 issue 1 dated 1980 (1st ZX81 came out in March 1981) (3 photos attached) I've got a few questions you might be able to shed light on (referring to the photos). ZX81 Variations ZX81 Chip Pin-outs ZX81 Video Transistor Amp Standby alert Using edges of the Z80 clock signal. But after leaving it for a few hours and coming back to try again, it worked first time - a cursor! Picture wasn't great, but I had a cursor. It is designed for maximum compatibility with existing software. Features The ULA may not have been unique as a ‘sea of gates’ customisable chip, but Ferranti’s CDI (Collector Diffusion Isolation) process was well-suited to the implementation in being able to Sinclair ZX81 ULA. 64 KiB) Viewed 10928 times. It had two There are 2 possibilities for the ULA chip: ULA2C184E or the newer ULA2C210E The older 184E doesn't have the back porch on the NTSC signal and many TVs display a very dark screen because of that. The memory for the Basic language was I have been getting my (kit built by me) ZX81 working again in the last couple of months. Sir, are you absolutely sure? It does mean changing the bulb However, it could also be a faulty ULA. but that is not the way it was The quickest way, is to have a working ZX81 that has all the chips socketed, so you can swap the chips from the faulty Zeddy to work out what is good and what is bad. Wouldn't surprise me if they layed out the internal circuits using pencil Sometimes the ULA, the Z80 CPU and the ROM are socketed. Which would be very unusual for an IC Sinclair ZX80 / ZX81 / Z88 Forums. One thing that was annoying was that it had a missing rubber foot (you can see it when I type the Shift-P in The ULA may not have been unique as a ‘sea of gates’ customisable chip, but Ferranti’s CDI (Collector Diffusion Isolation) process was well-suited to the implementation in being able to I'm not aware of any other ULA replacements. Uses two 20V8 and four 16V8 chips (both readily and cheaply available), and a '374 latch. ZX81 Chip Pin-outs ZX81 Video Transistor Amp The ULA is basically a lot of Logic condensed into one chip to save production costs and this board replicates the ULA with a lot of 74 Logic. ZX80 / ZX81 hardware and software offered for sale or swapping. The oscillator runs at 6. Discussion forums for users of the Sinclair 8-bit range of computers - ZX80, ZX81, ZX Spectrum, Z88, clones 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. Part Type. Joe I think I have the rest of the components already. 2. Skip to content. It was designed to replace most of the discrete logic chips of the ZX80 Learn how to use the ZX-Key ZX81 Interface, a PCB that connects a modern keyboard to a ZX81 computer. There is a copy of the issue two schematic here. Sinclair ZX81 ZXVid - Composite Video/ULA Fix (self-fit) Mark. It’s only with advances in semiconductor technology that chips have been manufactured that run cool for the same operating frequency. Anyway most "repair models" of ZX81/TS1000 have a broken ULA chip, I think. So either I need to go back really far to a VERY old TV (I'm guessing that means an old B&W CRT one) or upgrade my ULA chip which, it appears, may let me use any TV with a The 6. In order to get a K almost everything needs to be working. As this machine is already heavily modified, I swopped its ULA for a VLA81 modern replacement which has some display options broken out on dip switches (basically it emulates various versions of the ULA chip). I did measure the voltage of the power supply and it was 9. I replaced the ULA on my zx81 with one that brightens the video. 5 MHz Z80A 8-bit microprocessor from NEC, an uncommitted logic array (ULA) chip from Ferranti, and an 8 KB ROM providing a simple BASIC interpreter. This was a technology pioneered by Ferranti, of which Sinclair was one of the If it’s in a socket, as well as checking for for dry joints, broken/cracked tracks, also check the pins of the chip are clean, and that the chip pins actually make contact with the The Sinclair ZX81 was able to be manufactured at such as low cost largely due to the ULA - the "uncommitted logic array". I have a ZX81 that has the ULA, the Z80 and the ROM socketed, so that's handy. ULA Pin Assignments ULA Operation The ULA takes the 14MHz master clock feed on pin 39 (Q) An upgraded / replacement ULA for the Sinclair ZX81 is now available. And even if it did, that would not tell you which ULA version is in the machine. Search; TS1500 ULA pin location. dessony Posts: 354 Joined The ULA fitted in your unmodified ZX81 is this later type. 1024MAK Posts: 5353 ZX81 Variations ZX81 Chip Pin-outs ZX81 Video Transistor Amp Standby alert There are four lights! Step up to red alert. NAND gates, flip-flops, etc. I used Andys ULA as a start when making my three chip Zeddy using preprogrammed auto save ram (32k). With some signals, on some types of chip, the designer of the system, or the circuit board designer may not connect the pins as you may expect. A view of all the component parts that make up the ZX81 - Replacing the ZX81's ULA: Some background information on the ULA and links to some sites that have replaced it with discrete components: 13th January 2015 . ZX81 Clone ohne ULA Chip, nur mit Standardbauteilen. The good news is someone may have a machine that they upgraded the ULA in and they have the older ULA, presuming you want to keep it original. A gate array is an approach to the design and manufacture of application-specific integrated circuits (ASICs) using a prefabricated chip with components that are later interconnected into logic devices (e. vLA82 – Spectrum 48K ULA replacement. Before soldering in a 28 pin socket, I show which tracks to cut to isolate the upper four address pins for 62256 32K byte SRAM chips. Other than that, it’s a case of obtaining another ZX81 or TS1000 and using it as a donor machine. Bye bye summer 2024 I bought a ZX81 ULA replacement module from you. Attachments Top. ZX81 ULA logic isn't very complex - a few counters, a few flipflops, an 8 bit shift register, and some logic tying things together. Title Sinclair ZX80 / ZX81 / Z88 Forums. But before I do, I'm going to place a sticker in the case that states the ULA number. The entire machine The ULA chips used by Sinclair in the ZX Spectrum use two independent power pins. The heat generated by the ULA is now able to permeate the cool void sans 7805. As when the system is generating a display, it’s the Z80 that gets the display data. The ZX81 uses the Z80 to get the display file data to feed the parallel to serial shift register (part of the ULA), but also uses the Z80's DRAM refresh cycle to perform part of the work of generating the video image. If you do want to keep it original you will need a B&W analog TV to act as a display, as the older ULA does not like color TVs or newer TVs. There’s also some great projects and links on the Tynemouth site about building clones of the ZX81. Plus, it's the ZX81 display access that's the problem with the faster modern CMOS SRAM chips, not the normal read access. I recently got an old Sinclair ZX 16K RAM pack with no case and 7 out of 8 ram chips and ULA etc. However, the ZX81 ULA is smaller (the chip inside the package) and less complex compared to the ULA in the ZX Spectrum. It was popular during the upheaval in 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. PLD are 20v8. A compatible chip was made in Russia as T34VG1. This includes the master oscillator (master clock). If you suspect RAM, and have a 16k RAM pack ULA 2C210E seems a little cooler than the previous ZX81, running at 70C vs 78C the previous one did. You can download the install guide here. Because the ZX8401 does all the multiplexing for all the DRAM from the Z80A side, if this chip dies However, the ULA does not use the ZX8401 when reading the DRAM to generate the video The ULAplus™ specification describes an enhanced ULA for the Sinclair ZX Spectrum family of computers. It had write protect in the ULA for lower 16k. These are new ULA replacements created and manufactured by Charlie Ingley. A low for the sync low. Post Reply. Whether you want to just get a faulty ZX81 back up and running, or want to extend the ZX81 with expanded memory and ZX81 Chip Pin-outs Note the notch cut-out at the top of the chip. It’s intended for machines that came with two 2114 SRAM chips. The ULA is basically a lot of Logic condensed into one chip to save production costs and this board replicates the ULA with a lot of 74 Logic. ULA chips from Ebay via a seller called 'Retro Computer Shack'. The 2C210E and 2C184 ULAs (AKA the Sinclair computer logic SCL) is the ZX81's ULA. The difference between the two was the introduction of the ULA chip which reduced the number of components on the motherboard and it supports slow and fast mode, ie while typing or displaying text the screen does not blink as the new ULA was taking care of the display does The ULA does not have any memory location that can be accessed with PEEK. ULA 2C210E seems a little cooler than the previous ZX81, running at 70C vs 78C the previous one did. As well as the regulator ZX81 edge connector. While there is no easy way to extract radiant heat from the ZX81 case, the overall temperature level inside has vastly subsided. The first two versions do not produce a video signal that is fully compatible with colour TVs. ZX81 ULA-in-a-CPLD. What are the odds I have killed the chip? Is it more likely to be some other issue? I have another working ZX81 with socketed chips, but ideally I don't want to tempt fate and break that one in trying to repair this one. 663 to . That project required 6 chips including a 2K RAM chip. 78 posts Page 1 of 8. 25V? Building a ZX81 clone today with all new parts using the ZX81+38 PCB, with a stylish printed case and a tactile keyboard. 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. DIP; chip label 74HCT245; pins 20: IC2: 74HC245: DIP; chip label 74HC2T45; pins 20: IC3: AP1117E50G: 500mA; chip AP1117E50G; Voltage Regulator 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. On Vacation until the 27th of June. The part of the video signal that is not generated is called the “back porch” and this part enables a colour TV to determine the black level of the video signal, so that it I have the same ULA in my 1000. It’s common for issue three boards to have most chips soldered. (ULA) chip. but that is not the way it was implemented on the ZX81. The ZX81 used one, and the Spectrum used a different one. But in a Lambda, the ULA contains the pixel data for the character set. SINCLAIR LOGIC CHIP ( SCL ) PART 2 by Don Lamen, SINCUS 6-29-88 Simulation Circuits and Timing Charts of the SCL Chip Being unable to draw the exact circuits; because of the lack of any technical data on the Ferranti Mask Programmable Universal Logic Chip ULA2C184E (either ZX81 Variations ZX81 Chip Pin-outs ZX81 Video Transistor Amp Standby alert There are four lights! Step up to red alert. Brand new Zilog Z80 Central Processing Unit for Spectrum (and ZX81, Amstrad CPC etc) Modern lower-power CMOS version, direct replacement for NMOS originals. Whether you want to just get a faulty SCL is the Sinclair Computer Logic chip, customized on the ULA product line. The resonator, R4 and C6 are what you see connected to ULA pin 35. The normal temperature range for the actual silicon chip goes up to 125°C. I'm finally getting back into the ZX81 saddle after 35+ years, purchasing an "untested" issue 1 ZX81 from a well known auction site (I knew the risks but fancied a challenge!). A plug-in PCB module designed to replace the ULA chip found in UK Spectrum 16/48 motherboards (versions 2 to 6) - Here's some fitting notes. The Lambda 8300 was a Sinclair ZX81 clone from Lambda Electronics Limited of Hong Kong. ZX81 Chip Pin-outs ZX81 Video Transistor Amp Standby alert There are four lights! Step up to red alert. 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. Oct 3 rd, 2007, 9:12am Timex Sinclair 1000 - ZX81 « ULA Replacement It sounds like his replacement for the ULA could indeed make ZX81 "badge" in just 4 chips! Lots of details to work out, though. It came with 1K of RAM, and 8K of ROM providing a simple BASIC interpreter. While all later issue 2 boards did. Print view; Search Advanced search. With a ZX81/TS1000, a black screen is normally caused by the ULA or its associated support components. The web page explains the interface components, power I was reading that the ULA in the ZX81 effectively replaces discrete logic chips such as 74LS IC's found in the ZX80, does anyone know how I can find out a logic schematic of the ZX81 ULA so Sinclair Research ported an enhanced ZX80 design to a ULA chip for the ZX81, and later used a ULA in the ZX Spectrum. With the ZX81 ULA, they did not have enough pins for this, hence the single +V supply pin. With the heat now taken out off voltage regulation, this leaves the ULA as the only other major heat source. Also a DKtronics replacement keyboard. Also visually inspect the ULA socket (using a good light and a magnifying glass) and the 6. Welcome, Guest. The computer was cheap in UK, it was available as DIY kit or assembled one. So the middle of the plastic DIL package getting too hot to hold your finger on, is normal. Apparently, Ferranti designed the ULA to run at around 50% utilisation, but the ZX81 runs it at closer to 75%. ZX81 Variations ZX81 Chip Pin-outs ZX81 Video Transistor Amp Standby alert There are four lights! Step up to red alert. Mark Meanwhile if you have a 'scope or a logic probe check the address lines going to the 74LS157 and the ULA, the multiplexed address lines between the 74LS157 / ULA and the 4116 DRAM chips, and the data lines going to the 4116 DRAM chips for "stuck" bits (lines that are always at a logic low or high level when they should be changing). One thing that was annoying was that it had a missing rubber foot (you can see it when I type the Shift-P in 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. Cheers everyone Dukester The early ULA in the ZX81 gave a poor TV display on a colour television (hard to see as the background was too dark), although a replacement ULA 2C210E gave a rock steady display. There are lots of cheap NTSC monitors on ebay ZX81 ULA-in-a-CPLD. On a ZX Spectrum 128, or ZX Spectrum +2 the ULA is the Ferranti 7K010E (later labelled Amstrad 40056) . I'm trying to diagnose a couple of issues but am increasingly beginning to think I may have a ULA (2C184E) issue: The ZX81 then reduced that number to 4. Description. 95V to the matrix cells. will need all the help it can get as the thermal resistance from the ULA 'chip' itself to the heatsink will probably be quite high. Unfortunately, like most of the ZX Spectrum schematics, there are numerous errors and mistakes. Follow edited Sep 20, 2017 at 11:34. 2022 by cg. Quick links. Circuit diagram lost at the moment, but could be largely recreated if you are very familiar with the ZX81 circuit. Search Advanced search. Label. Cosmetically, there are a few scratches and the red paint is mostly worn off the embossed ZX81 logos on the computer and memory pack, but it's not too bad. He especially likes them fitted on hot ULA chips inside a nice warm Zeddy with hardly any airflow so that the ULA can continue to cook nicely without compromising speed. Three of the four rubber feet were missing. 78 posts Page 2 of 8. 7,354 17 17 silver badges 33 33 bronze badges. The ULA chip, described by the ZX81 manual as the "dogsbody" of the system, has a number of key functions that competing computers share between multiple chips and integrated circuits. Tribute site for the Timex Sinclair 1000/1500 and ZX81. This site has been setup to facilitate users to be able to purchase aftermarket goods from suppliers at a value for money price point. And you say that the board that you have is based on an issue 6A (which over here uses a 6C001E-7). Sir, are you absolutely sure? It does mean changing the bulb The naming of the pins on the chips is as per the manufacturers data sheets (except for the ULA, where I used schematic circuit diagrams and checked a real ZX81 issue 1 PCB). Sir, are you absolutely sure? It does mean changing the bulb Some issue 2 boards had the first ULA version chip fitted along with the cockroach. Plugin ULA replacement. Providing the functionality of both the earlier 2C158E/184 ULA (without back porch) and the The ZX-ULA2 is a direct replacement for the standard ULA used in the Sinclair ZX81 home computer. Mark. The ZX81 video hardware consists of the Z80 CPU, ROM, RAM and the larger part of the ZX81 Sinclair Logic Chip (usually called the ULA) as shown in FIG 1 with all relevant connections including the isolation resistors R. Pin 14 supplies the peripheral cells with a 5V supply. If you want to add extra's like clock doubling ZX81 ULA replacement revisited. After a quick chat I managed to secure one of these ULA chips for myself and quickly set ZX81 Variations ZX81 Chip Pin-outs ZX81 Video Transistor Amp Standby alert There are four lights! maybe it's marginal; not sure. Is your ZX81 using an original ULA chip or are you using a replacement module such as a vLA81? Mark. Doesn't mean my CPLD design behaves exactly like a Sinclair ULA! C4005 ULA I/O chip: Sound: C4005 (1 voice, 3 octaves) Input: Tape interface (audio in / out), expansion bus, Atari joystick port: Dimensions: 295 x 150 x 55 mm: Mass: 700 gr: Backward compatibility: ZX81: Back of Lambda 8300. This is of course thanks to the more advanced ULA chip the Spectrum has, which allows it to run at a faster speed whilst still showing the output to the TV. The Spectrum is similar except the ULA does more stuff (which can also be done with 74 series logic). On my blog, in this entry I show how I modify an issue 1 ZX81 PCBs so that a 32K SRAM chip can be put in a socket without having to bend any pins. 14 posts 1; 2; Next; mhudson52 ZX81 Chip Pin-outs ZX81 Video Transistor Amp Standby alert There are four lights! Step up to red alert. It's still in New York, and I'm in California. 25 MHz. Not seen hanging between pins of this mini-ULA either. ZX81 Variations ZX81 Chip Pin-outs ZX81 Video Transistor Amp IC1 is the ULA IC2 is the ROM IC3 is the Z80 CPU IC4, or IC4a and IC4b is/are the SRAM chip(s) The ULA runs rather warm. Which I think must mean that this mini-ULA includes some analog circuitry to create those delays. Can you please take some more photos at an angle showing the connections from each side. You want the “5C and 6C ULAs” diagram here. 25MHz, and has only 1K of onboard memory, with a 8K ROM chip containing The ZX81 powers on and produces a white screen on the TV, but i dont get the black cursor. Your best bet is to obtain a vLA81 (see also the link in an earlier post). In that case, adding a resistor (perhaps a few kOhm?) from ULA pin to ground may do the trick. The ZX81+38 is a clone of the Sinclair ZX81 home computer that replaces the ULA found in the original with standard logic ICs. It is less common to find the RAM chip(s) socketed. 5 MHz is the speed that the "clock oscillator" for the ULA operates at. The video output pin on the ULA actually outputs three voltage levels. And original ULA chips have not been manufactured for decades. Address lines & Data lines seem to be sending data. Sir, are you absolutely sure? It does mean changing the bulb There are only three other onboard chips: a 3. Improve this answer. Released in 1981, the Sinclair ZX81 — known as the Timex ZX-81 and later the Timex Sinclair 1000 in North America — was Sinclair Research's even more affordable follow-up to the Sinclair ZX80, based around the same eight-bit Zilog Z80 processor but with a dramatic reduction in component count thanks to heavy use of a single Ferranti If the ULA is in a socket, and you get a strange reading, try carefully removed the ULA. This 40-pin integrated circuit, a Ferranti "ULA2C184E or Ideal for installing in an aftermarket Spectrum PCB without needing an original ULA. 5MHz oscillator or "clock". The aim of this project is to build a ZX81 ULA equivalent circuit using discrete components that are readily available. Not present on any pin of this mini-ULA, not even via-via. Myself, I've not had the on board 1K RAM chip(s) fail. In addition to the normal ZX81 non-inverted video pattern for each character, the circuit generated additional tables of video patterns for the inverted characters (CHR$+128). 5 MHz clock, from which a 3. VSHF. 3D Printed ZX81 Rubber Feet. First off, have you checked that the +5V supply from the 7805 voltage regulator is between 4. The vLA82 is a modern plugin replacement for the Spectrum 48K ULA (type 6C001E-7 or earlier). PLD are 16v8. 1. Whether you want to just get a faulty The ZX81 ULA is a custom gate array that handles the screen, keyboard input, memory access and tape input/output. This part was used, as it was cheaper than a quartz crystal when the ZX81 was designed. The internal voltages (such as on ULA pin 16) are designed for the modulator and are not standard composite video signal levels. A 64 macrocell will probably do if all you need is a 'vanilla' ZX81 ULA replacement. Unanswered topics; Active topics; Search; FAQ; Login; Register; Board index. Sir, are you absolutely sure? It does mean changing the bulb Is it ok to test the issue 2 ULA 5C112E in the issue 3 board to check it is working. Im getting the 3. PLD, ZXLNC2. Conversely, the ZX81 has two commands the Spectrum doesn´t: SLOW and FAST. This is because the Z80, the RAM, the ROM and the ULA together are all vital to producing a screen display with any pixel or text information. The Z80 runs slightly warm. The ULA was the reason the ZX81 was inexpensive yet as powerful as more expensive early home computers. Ram & Rom Clock is pulsing There are also slight differences with the output voltages from the ULA chip, even the same types. Sir, are you absolutely sure? It does mean changing the bulb Look for ula. I couldn't replicate that, so I am sticking with discrete logic chips. GBP 5 more expensive (different chip ) and will offer Clock doubling, inverse video, inverse border, M1not, and a constant 3. Joined Jan 22, 2011 Messages 6,647 Location Vancouver, BC. A Xilinx XC9536, that works at 5V: €3,87 A PLCC44 to DIP40 adapter board: €1,36 The sum of this hardware is: €5,20 It also depends how the pins on the adapter board is mapped. Some issue 2 boards did not have the spider fitted. 5 MHz Z80A 8-bit microprocessor from NEC, an uncommitted logic array (ULA) chip from Ferranti, and an 8 KB ROM providing a simple Sinclair BASIC interpreter. 11. However the ULA in your photo of your modified ZX81 has another chip soldered on top, so I can’t see the ULA type number/code. Sir, are you absolutely sure? ZX81 Chip Pin-outs ZX81 Video Transistor Amp Standby alert There are four lights! Step up to red alert. ZX81 Chip Pin-outs ZX81 Video Transistor Amp Standby alert There are four lights! Step up to red 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. No modification to the ZX81 circuit board should be allowed, and the only The vLA81 is a modern plugin replacement for the ZX81 ULA. It has a new sockets for the chips (except the 2114 SRAMs - planning on upgrading to a 16k or 32k SRAM at some point), new Andy ULA and freshly programmed EEPROM. It is a custom chip which contains most of the logic of the ZX80 with some additional logic to provide a SLOW mode which allows the zx81 to provide a display while still being able to provide limited processing power. ZX81s had either two 18-pin 1k x 4 bit SRAM chips (making a total of 1k x 8 bit = 1k byte) or a single 24-pin 1k byte SRAM chip. Mark Other than the cost reduction and simplification of the ZX81 into essentially a 4 chip computer, the main aim was to get rid of the flicker whenever a key was pressed or code was run. That means, it can be built with all parts still readily available today. 25 MHz clock is derived for the processor; Note that in a working ZX81 standard (as from the factory) computer, using a Sinclair PSU, the 7805 and it’s metal heatsink will get very hot (too hot to hold your finger on), the ULA chip will get hot in the middle, and the Z80 (or equivalent) processor will get warm (but not hot). 25Mhz output for people with zonx or other sound cards that need the clock. So I think someone wants to sell a complete (working) model rather than the heart of ZX81/TS1000. Jump to page: ZX81 Variations ZX81 Chip Pin-outs ZX81 Video Transistor Amp Standby alert There are four lights! Step up to red alert. Quote; Post by Moggy » Thu Aug 03, 2017 8:32 pm. Ram & Rom Clock is pulsing 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. So where the old ZX81 has ULA,CPU,ROM and one or two RAM this has a lot more hardware. PLD and ZXDECOD. I look forward to 1024MAK's reply about the ULA differences if he can point me to them. I've got some 2K SRAM chips to try, as well as 1 x 32K The ULA in a ZX81 is essentially all of the glue logic in one chip. 238 fluctuating. The ZX81 has two versions of the ULA: The video circuitry on the ZX81 is quite sloppy in its implementation of a video signal and many modern LCD TVs will simply refuse to When looking at the different solutions for a ULA in this thread, I came across these cheap parts that might work together for at ULA replacement. The ULA contains all the counters and logic to create the /NMI pulse, but the /Wait signal was On the ZX81, when the ULA that functions as the video chip is generating display output, it takes the character cell byte (that the CPU was tricked into fetching as an opcode) and combines it with an internal 3-bit counter, to generate an address to access the font in ROM and fetch a byte of bitmap. There are three different versions of the ULA chip used in ZX81 computers. Or indeed, any fault that causes the Z80 to execute random code rather than running the ROM code. 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 ZX81 then reduced that number to 4. 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. 50/60Hz mode switch, composite video output with Zigg's back porch mod and 1080p60 HDMI output. Using some analog circuitry (simple RC-delays are common). Anyway besides that sync thingy the ZX81 is fully functional: came with a 16 KB expansion (the owner made In a standard ZX81/TS1000 and similar computers, the ULA uses address line A15 to decide if it should override the data from the data bus with the NOP opcode. The other chip was an uncommitted logic array (ULA) chip from Ferranti which Sinclair advertised as their unique, custom-built, "master chip" which replaced 18 ZX80 chips. 028 - . Sir, are you absolutely sure? It does mean changing the bulb The ZX81 was launched in March 1981 as the successor to the ZX80. COMMENTS: SCL is another name for the Sinclair ZX81 ULA (specifically, SCL is the name used by Timex/Sinclair). This will allow me to use the working original ULA to fix another more standard zx81. Low power consumption. The ZX Spectrum 16K/48K ULA went through multiple revisions and is either a 5C or 6C series Ferranti ULA. That's my project, the one I mentioned in the comment to my answer. The board is getting the 9v & 5v supply ok. Come to think of it. 25MHz, and has only 1K of onboard memory, with a 8K ROM chip containing There are 2 possibilities for the ULA chip: ULA2C184E or the newer ULA2C210E The older 184E doesn't have the back porch on the NTSC signal and many TVs display a very dark screen because of that. Bye bye summer 2024 The ZX81 is almost identical, except that 74 series logic is all smooshed in to a ULA. Oh wait, the ZX81 actually has a third command the Spectrum doesn´t have: UNPLOT. Unknown 18-pin ULA chip. I checked the ram chips, they all work and if the ULA also works there'll hopefully be 16K of ram. The difference between the two was the introduction of the ULA chip which reduced the number of components on the motherboard and it supports slow and fast mode, ie while typing or displaying text the screen does not blink as the new ULA was taking care of the display does The other difference I believe, is the character dot matrix data is in ROM on the ZX81, but in the "ULA" on the Lambda Mark. And a intermediate voltage for the black video level. The ZX81 has a display file which is treated rather like a serial file. Über die ZX80/ZX81-Grundfunktionalität hinaus bietet die Schaltung. 1024MAK Posts: 5376 ZX81 Chip Pin-outs ZX81 Video Transistor Amp Standby alert There are four lights! Step up to red alert. Spektre Spektre. I have a few other ZX81's and T-1000's I will convert when I know which mod for which ULA. Sir, are you absolutely sure? (one) or a replacement ULA (one). The entire machine weighs just 350 grams (12 oz). The project offers various implementations: both FPGA friendly (with separate input and output data buses), and CPLD ready, to be used as a replacement for the many chips that comprise the ULA found in some clones. Ideal for preserving the original ZX81 ULA. Sir, are you absolutely sure? It does mean changing the bulb Autumn is here. Excellent replacement for ZX81 ULA chip. As you are removing a working ULA chip, these have value. Three different RAM chip types were used. ZX Spectrum's appear to have more ROM faults, but then, I am only going on a limited number of reports from the WoS forum. ZX81 Firmware. The ZX81 ULA does not contain the pixel data for the character set, as in the ZX81, this is contained in the ROM. Purchased item: vLA81 Sinclair ZX81 ULA Replacement The ZX81 is both simple (not many chips) and blooming complex all at the same time. This is the chip that replaced most of the motherboard logic of the ZX80. 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. So when the generated So that then leaves a very strange ROM chip fault, or a ULA chip fault. Last edited by PokeMon on Tue Jul 16, 2013 2:19 pm, edited 1 time in total. Must have for any retro computing fan willing a longevity for the good old original microcomputer hardware. If you have never removed a DIL/DIP chip from a socket before, ask for advice before doing so, as a bent or broken pin needs to be avoided. 5MHz resonator (X1). PLD and ZXSTATE. There are only three other onboard chips: a 3. As well as this, they solved one of the main problems with the ZX80. He sells brand new On Vacation until the 27th of June. Everyone else, Also, I have the ULAs bearing 184 and 210. And the ZX81 BASIC does not have either the IN (INP) function or the OUT command. ) according to custom order by adding metal interconnect layers in the factory. A faulty ROM, RAM or processor will cause a white screen, as the ULA produces white unless instructed otherwise. For both the above reasons, a 100µF (although the actual value is not critical) capacitor is normally used to AC couple the signal, while blocking the DC levels. Sir, are you absolutely sure? The ZX81 powers on and produces a white screen on the TV, but i dont get the black cursor. Brand new reengineered incarnation of a proprietary technology not produced anymore from original vendor sources. could that be a source of problems? falter Veteran Member. Sinclair ZX80 / ZX81 / Z88 Forums. The PCB tracks need a lot of work and it seems to have had a major power event causing the 1N4148 diode leg to overheat. I'm still waiting for the delivery of my ZX8-CCB. Share. 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 Tested with an extensive suite of ZX81 software. Sir, are you absolutely sure? The ZX81 then reduced that number to 4. The replacement ula includes circuitry to directly drive the composite video The heart of the ZX Spectrum series of computers is a custom chip called the ULA (Uncommitted Logic Array). All buzzed out fine before inserting the chips. So, as far as I am aware, all stocks of the original ULA chips are sold out. ZX81 with Andy's replacement ULA - displayed image. Leave out the RF modulator, and just provide NTSC output. ZX81 Chip Pin-outs ZX81 Video Transistor Amp Standby alert The ZX Spectrum motherboard is fairly straightforward by modern standards: Integrated Circuits Most of the chips are soldered to the board, with the exception of the ROM and the ULA Discrete Component Values I’ve highlighted the most common parts that fail and may need replacing during ownership Note: Please note The board pictured (an Issue 2, 48K) is the model that I 1024MAK wrote: ↑ Sun Aug 08, 2021 11:33 am I can’t think of an easy way unless you have an expensive logic analyser with enough inputs to trace all the signals on that ZX8401 chip. ZX-Key Expansion Interface Main PCB Layout: Assembly List. 5MHz. Bye bye summer 2024 Sinclair ZX80 / ZX81 / Z88 Forums. ZX81 ULA's were designed & manufactured before first VHDL standard was even released. On some of the recreated modern ULA modules, often the crystal oscillator circuit pin is either unused, or used for an additional function, as these modules often have their own crystal oscillator on board. Andy was demonstrating his ULA chip replacement which has the ability to double clock the old 81 and the results were really impressive. bit keeper is a weak feedback inside the io buffer of the xilinx chip it will retain the last known logic level on inputs without sufficiently strong pull-up / downs. And can you please With NMI generator enabled as on a ZX81, things are 100% working and I was unable to find any software that worked different than on a ZX81 with Sinclair ULA. Sir, are you absolutely sure? But the 5C ULA chips have less compatible DRAM timing compared to the 6C001E-7. 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 ULA (Uncommitted Logic Array) is a chip which controls most of the interfaces between the Z80 CPU and peripheral functions. 5 MHz. Looking forward to 2025. resistant Kapton tape over the pins on that side of the chip, it should protect against accidental solder splash but it will melt under sustained application of heat. Not had a ROM fault yet on a ZX81. 75V and 5. answered Sep 20, 2017 at 11:26. I don't have another ULA or another ZX81 to test my TV sets (they work perfectly with ZX spectrums tough). Title On Vacation until the 27th of June. RAM Chip - . Sir, are you absolutely sure? For example, the pixel shift register is in the ULA. ZX81 Variations ZX81 Chip Pin-outs There are only three other onboard chips: a 3. vLA82 1. And the CPU generates addresses which the ULA uses to look up the characters' bitmaps from the ROM (Yes, I know the actual Chip selects are generated by the ULA; luckily they're independent of whether it knows it is expecting a character graphic. Top. All chips are getting thier 5v supply. Sir, are you absolutely sure? It does mean changing the bulb The ULA chips fitted in the ZX81, TS1000, ZX Spectrum 16K/48K/+ are working within their designed temperature range. For simplicity only the 2K RAM is shown. Timex 1000 machines had a single 24-pin 2k byte RAM chip. Having an extra chip mounted on top is unusual. 731 - assuming I'm doing this correctly this is really odd? I'm not sure how to find the centre pin of the RCA jack. Can you please tell me where the red and blue wires go on the ZX81 board, or post up photo(s) showing this. Komponenten). the silicon chip count was reduced to only 4 by cleverly combining 18 of the ZX80's chips into a single ULA chip (Uncommitted Logic Arrray). Then you have computers like the H89/Z89. I have a dandanator to run the zx diagnostics. The ULA getting hot is perfectly normal. and realized the ula chip handled cassette functions. And yes, the ROM socket being 28 pins but with a 24 pin chip fitted is normal. At the RCM weekend I met up with SirMorris and a guy called Andy Rae and was introduced to the crazy world of the ZX81. Discussions about Sinclair ZX80 and ZX81 Hardware. It combined the ZX80's video circuitry and an NMI generator into a single chip, thus reducing the cost of manufacturing the computer. The ZX81 was based around the Z-80A CPU which ran at 3. Sir, are you absolutely sure? It does mean changing the bulb Bah humbug, it’s the winter. v file which is code representing ULA chip by FPGA. With the ULA back in the correct orientation the system only starts to a white screen now. Sir, are you absolutely sure? Before I buy one though, I think I need to get clear on what TV I need, as I have the ULA chip referred to below (2C184E) which apparently doesn't work with many modern TVs. I was doing some reading on the zx81. Sir, are you absolutely sure? Hi guys, I have a ZX81 that have an old ULA (ULA2C184E) and I have problems connecting it to all TV sets I have, I get a very dark, blurry and noisey image, you can barely see something turning the bright all the way up. It can be implemented as a plug-in replacement for the ULA such as SLAM+, an external interface such as ZXHD or MB03+, in emulators, or in modern clones such as the ZX-Uno. ZX81 Variations ZX81 Chip Pin-outs ZX81 Video Transistor Amp Standby alert There are four lights! Step up to About the ZX80 / ZX81. The SCL Chip is designed around a Universal Logic Array (ULA) made by Ferranti. zx81user Posts: 54 ZX81 with ZiLOG Z84 CMOS Z80, 32KB battery-backed Toshiba 55257 SRAM with charge status LED, Wilf's "Why Wait?" mod and switch-mode 5V regulator. The ZX Spectrum +2A, +3, vLA81 : A replacement for the Sinclair ZX81 ULA (R1 to R6 at 4. ZX81 Variations ZX81 Chip Pin-outs ZX81 Video Transistor Amp Standby alert ZX81 Chip Pin-outs ZX81 Video Transistor Amp Standby alert There are four lights! Step up to red alert. RWAP Posts: 1349 Joined: Thu May 08, 2008 8:42 am Location: Stoke-on-Trent, UK The issue one board was hand drawn and there are no known issue two ZX81 boards. [13] Acorn 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. 16 I measured the ROM and RAM chips to start and got weird readings as well. However, the keyboard Well, if you fancy a long read about how to recreate the ZX81 ULA using 74 series logic gates, then boy do I have a link for you: Like the ZX80/1, there's a support chip handling some of the heavy lifting for video display, but it had to be managed by the CPU to an almost comical degree. . 5MHz appropriately. Inside the ULA this clock speed is halved (divided by 2) to 3. Please Login or Register. There are few peculiarities on the board: big cooler on ULA, unusual spider mod and something that looks like extra audio output. Computer draws about 320mA when running. A high for peak ‘white’ video. Definitely don ZX81 Variations ZX81 Chip Pin-outs ZX81 Video Transistor Amp Standby alert There are four lights! Step up to red alert. It was popular during the upheaval in Part 1 of this two part series documents one possible way to perform a DIY composite video mod on a ZX81/TS1000 with the newer ULA 2C210E, as opposed to the older ULA 2C184E. The main change between the ZX80 and the ZX81 was integration of all the logic into a single ULA chip. Disassembly of ROM code and other firmware-related articles. They use a type of technology that generates a lot of heat. If you want to add extra's like clock doubling The ZX81 was the successor of the ZX80 and was sold in two forms as a kit and assembled version. These parts and the circuitry in the ULA form the 6. There is a Ferranti ULA chip, the NEC Z80 processor, a Sinclair ROM, a couple small RAM chips, and some support logic. So a larger capacity modern logic array chip would Starting with ZX81 #1, I fitted this with the newer ULA, initially without success. Last night I started desoldering the sockets from ZX81 #2. Timing-sensitive demo's, stuff that writes in the border area etc included. 25mhz clock out of ULA on pin 14 and its reaching the Z80 on Pin 6. of course to use these features 5 extra wires need soldering to connect the address lines that are not present Voltage of the ULA pin 16 is fluctuating from . Pin 1 can also be designated by a white dot marked next to it. Once again, designed by Rick Dickinson the ZX81 is based around a Zilog Z80 chip running at 3. g. The SRAM varies depending on the type fitted. ZX81 had no moving parts - the keyboard was membrane-based, there was no power switch or advanced outputs. So this block wasn't destroyed. Sinclair ZX81 ULA. The ULA is a custom chip designed by Sinclair Research Limited and is The ZX81 ULA replacement is a plug in pin compatible clone of the original ZX81 ULA with a bit of an extra boost. 7k - Some older Boards) ZX81 Interface Card Assembly. Discussion forums for users of the Sinclair 8-bit range of computers - ZX80, ZX81, ZX Spectrum, Z88, clones Enhanced version will be approx. If you use Andy's replacement ULA, yes you can run the Zeddy at 6. The ZX-ULA2 is a direct replacement for the standard ULA used in the Sinclair ZX81 home computer. The memory for the Basic language was So, the ULA uses a ceramic filter known as a resonator (X1 on the schematic) to form part of an oscillator. Sir, are you absolutely sure? It does mean changing the bulb The early ULA in the ZX81 gave a poor TV display on a colour television (hard to see as the background was too dark), although a replacement ULA 2C210E gave a rock steady display. [Side note, I never did understand why they included the keyboard input lines in the ULA for the ZX81, or the ZX Spectrum, having one extra inexpensive 74LS chip to handle the keyboard would have freed up four or five ULA pins]. Mark I was reading that the ULA in the ZX81 effectively replaces discrete logic chips such as 74LS IC's found in the ZX80, does anyone know how ideally what I am after is a blown up image of the ULA chip with the relevant circuit or logic symbols drawn within it, I will attempt it ZX81 Chip Pin-outs ZX81 Video Transistor Amp Standby alert There are four lights! Step up to red alert. One clone has several 74xx series chips to replace the ULA – if you like the retro DIP look. Further info can be found here. 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. Otherwise (like in the Sinclair ZX81 design) both are fed via the same power pin (the ZX81 ULA only has a single positive power supply pin). Work on the ZX81 hardware began in September 1979, even before the launch of the ZX80, but it was the development of the uncommitted logic array, or ULA, which allowed the machine to go into production. It's just RAM chips on the Zeddy that you have to watch out for Mark. It’s nothing to worry about. (ZX81NU - ZX81 Clone ohne ULA - PCB - Leerplatine mit hoher Qualität. Discussion forums for users of the Sinclair 8-bit range of computers - ZX80, ZX81, ZX Spectrum, Z88, clones About the ZX80 / ZX81. PLD, ZXNMI207. ULA 2C210E ROM Chip RAM Chip Z80 CPU 7805 Voltage Regulator. 25 MHz and then fed to the Z80 CPU via a buffer transistor. On the ULA, pin 35 is the connection to the ceramic resonator. The design incorporates a thin PCB ‘shim’ between the 32K ram chip and the socket. This is an implementation of the Sinclair ULA chip, found in ZX Spectrum microcomputers. [1] [2] The ZX81 motherboard is quite simple by modern standards The main chips have been highlighted: The ZX81 I own contains 2 x 2114 chips, so you will see how they fit on the board in my blog posts. jpg (10. The PCB does the simple job of rerouting a few pins to the right place and has no active components. These comprise the following: Synchronising the screen display; Generating a 6. vLA81 installed in an issue one ZX81. ZX81 ULA. The internal semiconductor junction temperature can be up to 125°C (even higher for some devices). Ian of Mutant Caterpillar may still have some, but will only fit them as a repair due to being unable to Ideal for preserving the original ZX81 ULA. Other than the cost reduction and simplification of the ZX81 into essentially a 4 chip computer, the main aim was to get rid of the flicker whenever a key was pressed or code was run. So is it an original version 1 ZX81? 2) The main chips are socketed. 7 posts • Page 1 of 1. Any discussions related to the creation of new hardware or software for the ZX80 or ZX81. So the Z80 CPU in a standard ZX81 operates at 3. It is one of several ULA replacements I have made for members of the Sinclair computer The ZX81 was launched in March 1981 as the successor to the ZX80. 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. The ULA in the ZX Spectrum can generate a display with no CPU help whatsoever. Among all the components on the ZX81 circuit board, the ULA especially was known to run hot and is a common point of failure in these machines. I don't recommend testing here, as loading by connecting test gear may stall the oscillator. The downside to this is that it got extremely hot due to the electronics being packed so densely. Hardware. I will be placing heat sick paste on the ULA before I put my system back together after the mod. ocrayl xbthnv bkyz wql zkpht jlcltkex yoh vxaoxme hdw ghdi