95 Replies Latest reply on Mar 26, 2019 4:44 AM by COMPACT

    Is anyone interested with the Z80?

    COMPACT

      The Z80 is still manufactured today and I was wondering whether there is any interest for a community or discussion group.

        • Re: Is anyone interested with the Z80?
          Andy Clark (Workshopshed)

          I did learn on the Z80 but rarely venture into assembly now so would have little to contribute but I'd probably follow along with interest.

          • Re: Is anyone interested with the Z80?
            michaelkellett

            What sort of things would you discuss - Z80 has such poor performance compared with modern processors that surely no one would use one in  a new project ?

             

            MK

              • Re: Is anyone interested with the Z80?
                COMPACT

                Would you believe the Z80 is still in production today?

                • Re: Is anyone interested with the Z80?
                  brotherbob

                  I haven't kept up with modern processors but suspect they can't match the interrupt capabilities of the Z80, and interrupts can really make a design sing.

                    • Re: Is anyone interested with the Z80?
                      COMPACT

                      G'day Bob!

                      Yep, the Z80 has 3 interrupt modes.

                       

                      IM0, IM1 and IM2.

                       

                      IM0 (Interrupt Mode 0) is exactly the same as the 8080 where the interrupting device places a CPU instruction on the data bus during an Interrupt Acknowledge cycle. This instruction is usually a singly byte RST instruction but  can be any instruction one wishes. Not often implemented by hobbyists due to the additional hardware involved.

                       

                      IM1 (Interrupt Mode 1) is just a simple RST 0038.  When and interrupt is asserted the CPU calls the routine at memory address 0038H.

                       

                      IM2 (Interrupt Mode 2) is popular for hardware designs with Z80 peripherals such as the PIO or CTC are present. To get this working, the programmer must firstly set the CPU's I (Interrupt Register) as the Page number (i.e. the most significant byte) of where the nominated 16-bit Interrupt Service Routine addresses will be placed, secondly configure the supporting peripherals to generate the required interrupt vector (i.e. the least significant byte of the address) to fetch the ISR address, and of course execute IM2 and EI (Enable Interrupt) instructions.

                       

                      Upon exit from an ISR it is usual to perform an EI, RETI combination.  The Z80 is configured so that the EI instruction does not become effective until the completion of the following (usually a RETI or RET) instruction.

                       

                      However nested prioritised interrupts can be supported with the insertion of EI, NOP instructions at the beginning of ISRs but appropriate management is required to ensure correct operation.

                      4 of 4 people found this helpful
                  • Re: Is anyone interested with the Z80?
                    COMPACT

                    More on the Z80 vs 6502 debate

                    1. The Z80 can run quite complex programs without any external RAM because of its relatively large number of internal registers unlike the 6502 which has just a few registers and is reliant on page $0 (00-FF) memory to provide full functionality.

                    This fact is great for Z80 test and servicing programs where faulty RAM can be easily detected.

                     

                    2. Comparisons of their clock rates are irrelevant because they both operate from different timing schemes.

                    The 6502 timing scheme makes it easy to accomplish shared memory access without any contention (but requires double speed memory to do so).

                    • Re: Is anyone interested with the Z80?
                      clem57

                      Yes, but what to do? Run CPM.

                      • Re: Is anyone interested with the Z80?
                        COMPACT

                        Did you know that the Texas Instruments TI-83 and Ti-84 calculators have Z80s in them?

                        In fact you can program them in Z80 assembly language.

                         

                        There's also one with a 68000!

                        3 of 3 people found this helpful
                        • Re: Is anyone interested with the Z80?
                          D_Hersey

                          Let's think forward rather than backward; I'll take an octonion vector processor, THX!

                          • Re: Is anyone interested with the Z80?

                            I would have an interest in such a discussion. I still build with them and have since the 70s. Still have handfuls of them to play with. Have made several dev. boards also.(I realize this is a very old post)

                              • Re: Is anyone interested with the Z80?
                                COMPACT

                                That's fantastic!

                                 

                                I found the Z80 to be an absolutely perfect tuition aid as you didn't need a computer to build a computer.

                                (However a PROM programmer comes in quite handy!)

                                 

                                The most simple Z80 configuration doesn't require any external memory and can blink LEDS and can also run as a pausable and resettable binary counter.

                                  • Re: Is anyone interested with the Z80?

                                    Making it run NOPS? Basically turns it into two 4 bit counters. I have some PCB designs made for that to use as sequencers.Clock as slow or fast as it can go!That's as simple as it gets. That should be the first thing everyone does with one.

                                    As a side note-you can buy the Z80 on Ebay for a little more than a dollar each.......The first one I bought in the 70s was way more than that! US supplier Jameco Electronics has the Z80 for 2.49 and also sells the interface chips for even more fun.

                                • Re: Is anyone interested with the Z80?
                                  DAB

                                  Hi Monte.

                                   

                                  I used Z80's back in the 1980's and used to have a bunch of them around, but with all the other processors now available, they are not something I would try to use today.  Too many support chips needed.

                                   

                                  Given the Cypress PSOC, I would start there instead.

                                   

                                  DAB

                                  • Re: Is anyone interested with the Z80?

                                    This is the circuit I made boards for sometime back to get people playing with them:

                                    z80nops.png

                                    4 of 4 people found this helpful
                                      • Re: Is anyone interested with the Z80?
                                        COMPACT

                                        As they say in Mortal Kombat - "Most Impressive!"

                                         

                                        For NMOS CPUS I'd use higher value pull down resistors to cater for the one TTL (or 4 LSTTL) load limit.

                                         

                                        If you put an 8 way dip switch in series with R1-R8 and a LED and current limiting resistor on the /HALT pin to VCC you can perform other programs.

                                         

                                        Here are some examples to try;

                                        11000011  C3  -> JP C3 C3 (continually loops at address C3C3 through C3C5

                                        01110110  76 -> HALT     (Turns the HALT LED on - and Address LEDS still change value (for REFRESH))

                                        00011000 18 18 -> JR (+18) similar to the NOP loop but in bigger steps.

                                        11001001 C9 -> RET

                                        11001101 CD -> CALL CDCD

                                        11010011 DB DB -> IN A,(DB) (If you hook up a LED and current limiting resistor to the /IORQ line to VCC - it should blink)

                                        10101010 10 10 -> DJNZ +10

                                          • Re: Is anyone interested with the Z80?

                                            Hopefully this thread will pick up and get some folks wanting to play. Doesn't have to be a serious endeavor and maybe we can all learn(or re-learn).

                                            It has been a few years since I played with these last, but may go drag some stuff out get started again. It's a nice break from the modern gear.......

                                            Thanks for your input-will try it out!

                                            3 of 3 people found this helpful
                                        • Re: Is anyone interested with the Z80?
                                          chuck.jenkins@gmail.com

                                          I have owned not to long a go, I had bought 2 used Sinclair computer, I had repair and trouble shoot. I only did basic programming, but then I no idea. They both stopped working.

                                          • Re: Is anyone interested with the Z80?
                                            COMPACT

                                            Did you know that the Z80 has different memory access timings for instruction fetches and standard memory accesses?

                                              • Re: Is anyone interested with the Z80?
                                                clem57

                                                No, can you site a URL to see?

                                                • Re: Is anyone interested with the Z80?
                                                  gdstew

                                                  I worked at Mostek maintaining the Fairchild Sentry testers used to test the Z80s when they first began to manufacturer them. The second computer I every

                                                  built (parts, pcb, solder) was the SDB-80 which was the Mostek Software Development Board for the Z80 with 16K bytes (8 - MK4116 16K bit) dynamic RAMs

                                                  which Mostek also made. The first wire wrap board I ever made was a 48K byte dynamic RAM board also using MK4116s that worked with the SDB-80. I can

                                                  tell you there were a bunch of happy technicians when we were told that Mostek would be second sourcing the Z-80 and even happier when we were told we

                                                  could buy SDB-80 kits and build them ourselves! Those were really fun days. I still have a Zilog Z80 in a ceramic package that says it was manufactured in

                                                  Dallas even though Mostek was actually in Carrollton a suburb in Dallas County just north of north-west Dallas.

                                                  2 of 2 people found this helpful
                                                    • Re: Is anyone interested with the Z80?
                                                      clem57

                                                      Are you still in the Dallas area. So am I.

                                                      Clem

                                                      • Re: Is anyone interested with the Z80?
                                                        COMPACT

                                                        Wow! that's amazing that you got such a large DRAM board working with Wire-wrap.

                                                        Do you still have any photos or schematics of it?

                                                         

                                                        It was quite rare to come across Mostek parts in Australia. We usually got Zilog, SGS and Sharp.

                                                        And from memory the SGS parts didn't support the undocumented instructions.

                                                          • Re: Is anyone interested with the Z80?
                                                            gdstew

                                                            No photos but the schematics were from a Mostek Z80 application note which I may still have. I used a tool from Vector called the Slit and Wrap which used

                                                            small spool of wire coated with a soft insulator kind of like magnet wire that was slit by the wrap bit just before it was wrapped on the post. It was a great tool

                                                            for speeding up wire wrapping with one fatal flaw. If two wires pressed against each other hard enough, they could displace the soft insulator and short.

                                                            When ever I powered it up and it did not work I would have to look for two wires pressed against each other in a rats nest of wires (actually I was more

                                                            systematic than that but there were always problem areas) and separate them. When the offending wires were separated it would usually make a distinctive

                                                            "plink" sound so I knew when I found it.

                                                             

                                                            I used the same tool and a Z80 to wrap up a 256 x 240 x 4 bit/pixel graphics display controller. The schematic was from Byte Magazine and I modified it from

                                                            the original 1 bit/pixel configuration and to use static RAMs that were fast enough to allow the Z80 full speed access to the video RAM by interleaving the

                                                            accesses with video timing generator. The Z80 assembly language software had to be entered in by hand to be assembled and of course modified to handle

                                                            the multi-bit/pixel mod and to use a 8 bit parallel interface to the SDB-80. I believe it only had commands for pixel read/write, line and circle drawing.

                                                            Unfortunately after quite a few sessions of find the Slit and Wrap short I gave up and disassembled it for the parts and never used my Slit and Wrap again.

                                                             

                                                            Like I said, fun (and sometimes frustrating) days.

                                                            4 of 4 people found this helpful
                                                              • Re: Is anyone interested with the Z80?
                                                                COMPACT

                                                                Ahhh!

                                                                 

                                                                The days of triple power supplies (+5, +12 and -12V).

                                                                 

                                                                Slit-N-Wrap from Vector.

                                                                It's still available today but not on the e14 catalogue.

                                                                 

                                                                I used a competing product called JUST WRAP and I think I've still got the blighter!

                                                                Ok Wire Wrap Jw-1-w Just Wrap 0.25 Daisy Chain Or Point To Point Nib Handheld

                                                                  • Re: Is anyone interested with the Z80?
                                                                    gdstew

                                                                    Yes, three voltage power supplies ruled then. And you can add +24V for the 8" floppy drives but they were usually in their own case with a separate

                                                                    +5V, +24V power supply. The MK4116, and all other dynamic RAMs of the time used +5V, +12V, -5V which was usually derived from the -12V which

                                                                    came in handy for  RS-232RS-232 drivers

                                                                     

                                                                    I thought it was Slit-N-Wrap but I couldn't remember so I went for the long version. I thought Vector was still around, I wonder if they fixed the shorting

                                                                    problem ?

                                                                     

                                                                    I remember the Just Wrap too and I know I was very interested but for some reason, lost in the mists of time, I never bought one which is made even

                                                                    more curious after all the Slit-N Wrap problems. I think I just went to pre-cut wire wrap wire (which I still cut to length) with an electric wire wrap tool but ...

                                                                      • Re: Is anyone interested with the Z80?
                                                                        dougw

                                                                        I still have a motorized Slit-N-Wrap and I still use it once in a while. It used to be really fast for wiring low-speed backplanes - much faster than manually soldering connectors on PCBs. I built a circuit that would make it automatically stop wrapping after 7 turns.

                                                                        I never had problems with shorts. They have 2 types of wire, one with a Tefzel (Teflon) jacket that is thicker than normal Kynar, the other is  a thin green enamel coating (a bit like magnet wire). I never had problems with either type although I was always careful not to let the green stuff rub on square pins.

                                                            • Re: Is anyone interested with the Z80?
                                                              balearicdynamics

                                                              A Z80 is still in production (incredible ) this guy has done an incredibly great job :The Z80 Membership Card Computer

                                                               

                                                              Enrico

                                                              1 of 1 people found this helpful
                                                              • Re: Is anyone interested with the Z80?
                                                                COMPACT

                                                                If anyone is playing with Z80s and CP/m be aware that Microsoft BASIC Compiler is only marginally faster than its interpreter sister.

                                                                 

                                                                The BASCOM and interpreter are 8080 based programs that are not optimised for the Z80.

                                                                From what I have experienced, the compiling a BASIC program results in a huge binary file that consists of the user's original BASIC program with keywords/tokens replaced with generic machine code mechanisms that call up rather large runtime library.

                                                                A simple (but fantastic) game like LADDER ends up being 40K in size when its Z80 counterpart is magnitudes smaller and efficient.

                                                                • Re: Is anyone interested with the Z80?
                                                                  Andy Clark (Workshopshed)

                                                                  For Specy fans, some interesting books

                                                                  1 of 1 people found this helpful
                                                                    • Re: Is anyone interested with the Z80?
                                                                      andrewj

                                                                      I volunteer at The National Museum of Computing in Bletchley (Milton Keynes).  For anyone who is interested, can move fast, and happy to donate to the museum, we have a ton of z80, 6502, Spectrum, ZX81, Commodore etc books we want rid of.  No lists, you’d have to visit.  It’s a good library to do some research into old machines.

                                                                      2 of 2 people found this helpful
                                                                        • Re: Is anyone interested with the Z80?
                                                                          COMPACT

                                                                          Many thanks for the offer but it's a little hard to pop in from Australia.

                                                                          Are you able to take a photo instead of a list?

                                                                           

                                                                          When I went to Bletchley Park a few years ago the Museum was closed.

                                                                            • Re: Is anyone interested with the Z80?
                                                                              andrewj

                                                                              Bletchley Park and TnMOC are completely different entities, albeit on the same grounds.  The museum is fully open Thursdays, Saturdays and Sundays and Colossus, Tunny, Heath Robinson and the Bombe are open every day.

                                                                               

                                                                              I can’t take photos unfortunately as the spare books are all boxed up, you’d have to visit - not practical from Australia granted!

                                                                              • Re: Is anyone interested with the Z80?
                                                                                andrewj

                                                                                I now have a list of books in excel format - partial list, more to come - available if you want to see it.  I can't see how I can upload it here, but I can always send it to you if you want.  They are now with anybook.biz for sale if interested and are a mixture of old technology books, including Z80, 6502, Spectrum, ZX81, Amiga, etc etc.

                                                                              • Re: Is anyone interested with the Z80?
                                                                                Andy Clark (Workshopshed)

                                                                                I've not been since the separation from the war museum, I suspect it's changed a bit since I was last there.

                                                                                  • Re: Is anyone interested with the Z80?
                                                                                    andrewj

                                                                                    I assume you mean Bletchley Park?  Not sure what was at TnMOC when you last came, but the Bombe is up and running in its new home with daily access - Tuesdays are engineering day so it may not always be running that day but you can still visit and get an explanation.  There is also an Enigma machine to support the demo.  EDSAC is pretty much done and going through its final tweaks: it can run a program but still some minor issues to resolve.  The Harwell Dekatron (WITCH) is in place and that’s a fascinating machine to watch, especially its decimal storage.  And of course Colossus, Tunny and Heath Robinson, the air traffic control display and all the 1980’s home computing machines you can play on - who remembers Manic Miner?

                                                                                     

                                                                                    At the moment the roof is being replaced and the large systems gallery is closed so you can’t see EDSAC or the WITCH (or the ICL and other large systems). Check the website for when that work is finished.

                                                                                    1 of 1 people found this helpful
                                                                              • Re: Is anyone interested with the Z80?
                                                                                shabaz

                                                                                I'm not deeply into the Z80 these days (apart from just general interest since it was the CPU in my first home computer), but there are some Z80 reference books here, although you've probably already got them or equivalent info:

                                                                                Index of /components/zilog/z80

                                                                                That site is great in general for all sorts of retro stuff from different manufacturers.

                                                                                2 of 2 people found this helpful
                                                                                • Re: Is anyone interested with the Z80?
                                                                                  weiwei2

                                                                                  i still have a z80 eval kit idling at my home corner, not sure what if anybody do use it nowadays but if got such a forum for modern revitalized usage of it, will be interested

                                                                                  1 of 1 people found this helpful
                                                                                  • Re: Is anyone interested with the Z80?
                                                                                    rob1512

                                                                                    I know the original post was a few years ago, but I decided to build a z80.  Is there anyone that is currently in a build. I'm not building a kit of anything and am starting to string it up on bread board until I get something working. Have a bunch of ideas but I'm sure they are not new, but new to me. I have experience in electronics and programming in assembler and c. Plan on writing my own os and bios, but will start with cpm. Or the Linux version that was on it . Forgot the name at the moment. 

                                                                                      • Re: Is anyone interested with the Z80?
                                                                                        COMPACT

                                                                                        G'day Rob!

                                                                                        I'm happy to observe and assist your with your progress in building a Z80 system from scratch.

                                                                                        I've done it many times to produce commercial (10,000+'s of units sold) and self interest projects.

                                                                                         

                                                                                        If you're using a solderless breadboard the first step is to get the CPU bootstrapped.

                                                                                        The first things to do is to get the power supply, clock circuit, and temporary reset circuit up and working.

                                                                                        The relevant CPU input pins must be pulled up or down as necessary.

                                                                                         

                                                                                        Your first program could be a LED flasher.

                                                                                        It consists of an LED with current limiting resistor connected to A15 with a 64K program consisting of just NOPs (0x00) that is hard wired to the data bus.

                                                                                         

                                                                                        Once you've got that up and going it's time to add a proper reset circuit and add a ROM and associated decoding and (POJ) Power on Jump circuitry.

                                                                                        If you're planning to work with CP/M you need to ensure that RAM occupies the address space from 0x0000 when in CP/M operating mode.

                                                                                         

                                                                                        One of the beauties of the Z80 is that you can have a RAMless system that runs useful programs.

                                                                                         

                                                                                        Consider a useful debounced and delayed response reset button circuit rather than an instant reset circuit.  This prevents an accidental touch of the reset button from resetting your system.

                                                                                        If you're very clever you may want to incorporate the patented "Special Reset" mode allowing you to run additional ICE (in circuit emulation) and testing software..

                                                                                         

                                                                                        If you're a purist, have a look at the system clock signalling requirements and ensure that your clock circuit meets the specifications.

                                                                                         

                                                                                        Good Luck!

                                                                                        1 of 1 people found this helpful
                                                                                      • Re: Is anyone interested with the Z80?
                                                                                        rob1512

                                                                                        Thank you. I have the z80 blinking address lines doing nops. Wired the ram and rom mod . Clock is working.  Build an eeprom written.   Hopefully put it all together  and flash some lights on the data bus tonight or tomorrow.  We will see.  I get side tracked easily. Lol .let the good times roll

                                                                                          • Re: Is anyone interested with the Z80?
                                                                                            COMPACT

                                                                                            Rather than flash lights on the data bus, why not have a separate port to do that by connecting an 8 bit flip-flop to the data bus with its inputs connected to data bus and outputs to LEDs and current limiting resistors and wire its CLK input so that any OUT instruction writes to it.

                                                                                             

                                                                                            1 of 1 people found this helpful
                                                                                          • Re: Is anyone interested with the Z80?
                                                                                            rob1512

                                                                                            That is what I'm planning. This is just the beginning. I was just starting where I was. I first thing I want to get accomplished is to get memory working and a serial terminal working so I can play around with it. This project will probably never be complete, but just further along . There is a lot of things I want to do but have to take it in steps. This weekend I want to get status LEDs set up. Reading and writing from memory, write an archaic is and watch what it can do. Then upgrade and upgrade from there.

                                                                                             

                                                                                            Was doing some thinking .I have transceivers between the CPU and the address and data buses. Is it necessary to have transceivers between the memory and the buses, since memory will almost always be involved in most of the bus usage, ie. Dma.? Dreams like there should not be too much draw on the bus keeping memory on it. The chips are only enabled when memory is being called for anyhow. They do you think?  

                                                                                            1 of 1 people found this helpful
                                                                                              • Re: Is anyone interested with the Z80?
                                                                                                COMPACT

                                                                                                Adding transceivers and buffers is a usual task for Z80 older designs when we used to use TTL.

                                                                                                The decision to use them depends upon the Z80 variant used.

                                                                                                I think the original NMOS variant can only handle  IOL=+2mA and IOH--250uA (1 TTL or 4 LS loads) whereas the CMOS variant IOL=+2mA and IOH=-1.6mA so ensure your design does not exceed these fanout limits.

                                                                                                 

                                                                                                If you plan to use DRAM with DMA, you'll need to ensure that all bus masters continue to refresh the DRAM but I'm guessing you'll be using SRAM.

                                                                                                2 of 2 people found this helpful
                                                                                                  • Re: Is anyone interested with the Z80?
                                                                                                    rob1512

                                                                                                    I started to use them but as a beginner, and using a breadboard(s), I opted to remove them as to the space, wiring, and debugging, was difficult . I will probably as them once I get a system running.  I'm getting really close . I have the z80 reading instructions from room and writing to ram.  I debugged that and to my surprise I worked after a few datalines crossed and a few address lines. Now working on the serial interface .

                                                                                                     

                                                                                                    I have a question,. Might sound stupid, but I am a beginner.  I have some full can crystal crystal oscillators . What is the difference between the full can 4 pin ones and the smaller 2 pins.  I've googled it and I must have the search terms wrong because I can't find an answer.  Do the full can ones have the capacitors built in?  The datasheet I have form them tells me nothing but the pinouts.   I've checked the output work my oscilloscope but I think the 7.3436? MHz is to fast for it and am not sure if I'm getting a sine wave or a distorted square wave.  I have some 1mhz coming in the next few days off the same style and I'll check them. Thanks.

                                                                                                      • Re: Is anyone interested with the Z80?
                                                                                                        COMPACT

                                                                                                        Hi Rob,

                                                                                                         

                                                                                                        Two pin metal cans are just crystals.  They require an accompanying circuit to make the them oscillate. The circuit can be as simple as two or three inverter gates with a couple of feed back resistors and a small ceramic capacitor.

                                                                                                        The voltage across an oscillating crystal is small and the accompanying circuit will output a suitable or near suitable signal.

                                                                                                         

                                                                                                        Here is an example circuit similar to that I used 35+ years ago.  For a Z80, it is also necessary to add a 330 Ohm pull up resistor to the output to meet the required clock input specification.

                                                                                                        You can of course use 7404 inverter gates in lieu of the 7400 NAND gates.

                                                                                                        Some variance can be used with the resistors. I've used 1K.

                                                                                                        C2 is just a ceramic (or monolythic) Coulomb bucket capacitor. (Others in correctly call it a bypass or decoupling cap but it's really there as a electron store because there's nothing being bypassed or decoupled).

                                                                                                        C1 is a trimmer pot allow the output frequency to be adjusted

                                                                                                        TTL Crystal Oscillator

                                                                                                         

                                                                                                         

                                                                                                        Four pin metal cans whether they be small or larger are often crystal oscillators.  It is the crystal along with the necessary oscillator circuit. Only three pins are used. Voltage, Ground and Oscillator output.

                                                                                                        To use it with a Z80 ensure that the output specifications are correct.

                                                                                                        Crystal Oscillator Pinout

                                                                                                         

                                                                                                        What type of Z80 are you using?

                                                                                                        1 of 1 people found this helpful
                                                                                                  • Re: Is anyone interested with the Z80?
                                                                                                    jomoenginer

                                                                                                    I've been reading Retro Gamer magazine for the past few months and the ZX Spectrum is reference quite a bit.  Sine the magazine is from the UK I suppose this makes sense, however until then I really had not heard of this unit until reading the mag.  Building a DIY ZX Spectrum would be interesting to play the old games on.

                                                                                                     

                                                                                                    There does seem to be quite a few projects for the Z80 on this website though:

                                                                                                    http://www.z80.info/homebrew.htm

                                                                                                    • Re: Is anyone interested with the Z80?
                                                                                                      rob1512

                                                                                                      I have a couple but I'm working with the z80b.  I have everything working with a manual clock along with a555 time clock running at 20 hz. Above that it is too fast to figure out what itit  doing .  The can oscillator i have is a 7.something. It will drive a baud generator on a serial interface, but I think it is too fast for the 6850.  I have a z8470 dart too and ordered a few things last night.  I might try timing a 555 timer to generate a baud need nothin more than 2400 or even 1200 at the moment.  I'm not sure how exact the baud generator needs to be to work with a terminal.

                                                                                                        • Re: Is anyone interested with the Z80?
                                                                                                          dougw

                                                                                                          What type of terminal?

                                                                                                          Early terminals were 300 baud.

                                                                                                            • Re: Is anyone interested with the Z80?
                                                                                                              rob1512

                                                                                                              Oh. Sorry . Just a terminal on my Linux machine. Not the old school dumb terminal .  Want to get that running so I can write a monitor program type of thing and load/ dump memory.

                                                                                                              • Re: Is anyone interested with the Z80?
                                                                                                                rob1512

                                                                                                                300 baud would not be too bad to start.  30sec to load a 1k program is faster than popping rom out programming it and putting it back in. 

                                                                                                                  • Re: Is anyone interested with the Z80?
                                                                                                                    COMPACT

                                                                                                                    What is the exact part number of the Z80 you're using?  It'd be like Z84xxx or Z84Cxxx for the later revisions.

                                                                                                                    This determines the electrical characteristics.

                                                                                                                     

                                                                                                                    Not essential but common baud rate generator crystal frequencies are multiples of 1.8432 MHz - this something that is easily divisible to get most or all of the common baud rates.

                                                                                                                    In the old days baud rate generator ICs (or Z80 CTC) would be used to divide this frequency down to the desired bit rate. (These days they're inbuilt into embedded micros).

                                                                                                                    With the above crystal a divisor of 6144 yields 300 baud, 192 yields 9600 baud.

                                                                                                                     

                                                                                                                    A good project to do is to write an X,Y or ZMODEM program to download and upload files.

                                                                                                                    2 of 2 people found this helpful
                                                                                                                      • Re: Is anyone interested with the Z80?
                                                                                                                        rob1512

                                                                                                                        I'll check when I get home tonight. According to the packing slip it is mk3880bn-l .But I'll check the chip when I get home. I do have a CTC I might try tonight. I do have 1.8432mhz crystal oscillators coming tomorrow.  Yes. I remember thoes protocols. Lol. Blast from the past. Lol. Anyway. I haven't had much time to work on it much this week,. I have been doing a lot of reading though on the various chips. Thanks.

                                                                                                                          • Re: Is anyone interested with the Z80?
                                                                                                                            COMPACT

                                                                                                                            With an NMOS Mostek Z80 (and with many others) with an oscilloscope confirm that the CPU Clock signal maximum is at least Vcc- 0.6V and below Vcc + 0.3V This is different to the standard Mostek NMOS Z80 signal levels of 2.0V.

                                                                                                                            It's stipulated on page III-72 of the Mostek Z80 Microcomputer Data book.

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                                                                                                                  • Re: Is anyone interested with the Z80?
                                                                                                                    rob1512

                                                                                                                    Omg. Doesn't sound like much, but I actually have a working serial interface working with basic working. Thanks for everyone's help but asking my somewhat dumb questions.

                                                                                                                     

                                                                                                                    Where do you people usually get your components and parts from?  I live in Connecticut, USA. I have been ordering from jameco. They are located in California.  Shipping is usually 4-5 days. Mouser is closer being in the mid West . Also digikey is in the same location. What area your experiences with these places or others in the us?  Shipping is usually $5 from jameco.

                                                                                                                     

                                                                                                                    Thank you again. I'm sure I'll have more questions, but I finally have something working and doing something. 

                                                                                                                      • Re: Is anyone interested with the Z80?
                                                                                                                        COMPACT

                                                                                                                        That's really quick to write your own BASIC!

                                                                                                                        Did you know that 8080 Microsoft BASIC was written on a PDP-10?

                                                                                                                         

                                                                                                                        Please post some pics, vids and schematic diagrams of your new system in action.

                                                                                                                         

                                                                                                                        I get many of my components from Element14!

                                                                                                                        I hunt around for obsolete components that are not stocked by Element14 but beware of Chinese counterfeits!

                                                                                                                          • Re: Is anyone interested with the Z80?
                                                                                                                            COMPACT

                                                                                                                            Hi everyone,

                                                                                                                             

                                                                                                                            I stumbled on these old beauties today,

                                                                                                                             

                                                                                                                            Good ole 68,000uF 16VW capacitors with screw terminals as used for S-100 Bus systems.

                                                                                                                             

                                                                                                                            These capacitors are the size of Soda Pop Cans and are used as filter capacitors for the unregulated +8V power supply.

                                                                                                                            Back in this era the power supplies were comprised of a giant transformer, full wave diode bridges and large filter caps.

                                                                                                                            Transformers had 3 sets of secondary windings. One for 8V with a large current rating (anywhere between 5-30A) and two 12V outputs with about a 1A current rating.

                                                                                                                            Every S-100 board had its own onboard voltage regulators that decanted power from the common -12V, +12V and + 8 V power supply lines.

                                                                                                                             

                                                                                                                            It could take next to forever for an unpopulated S-100 frame for the power to dissipate.  It was common to install bleeder resistors across these capacitors on test S-100 power supplies for faster power dissipation.