It's a great day when Ben Eater uploads

@ck84199

Жыл бұрын

What is he eating though?

@dennis8196

Жыл бұрын

​@@ck84199 chips

@MahBor

Жыл бұрын

@@ck84199 Silicon wafers, similar to those used in ICs

@gogs1606

Жыл бұрын

babe wake up, ben eater posted a video

@Jason62391

Жыл бұрын

​@@ck84199 bread board

A word of caution regarding the W65C51S parts. There’s a horrific silicon bug where the transmit buffer empty bit is stuck. Earlier versions of the datasheet mention this but the current version tries to sugar coat this issue. Shame there’s nobody else (that I’m aware of) making this otherwise very very easy to use part.

@NicolasGasnier

Жыл бұрын

That made me scratch my head for a long time until I found that info in forums. If I remember correctly, that makes interrupt driven data transfert useless. We are stuck with polling mode.

@Jenny_Digital

Жыл бұрын

@@NicolasGasnier more precisely, not only is Interrupt driven mode useless, but polling won’t tell you either. You have to wait however long it takes before just going ahead and transmitting the next byte.

@rafalklepinski7372

Жыл бұрын

Good to know. Might opt for the USB to UART cable using FTDI components to bypass this issue?

@argoneum

Жыл бұрын

And older Rockwell parts didn't have this bug… Hard to find a currently produced chip to replace the W65C51 though.

@eDoc2020

Жыл бұрын

@@rafalklepinski7372 That wouldn't help. The problem's with the UART itself, not the level conversion side.

This 6502 project series is really taking me down memory lane! I got started with a Heathkit H8 that was completely hand soldered, this was around ‘78 and I was in 7th grade. Me & pops build it over a weekend. My school chums had an Apple II which ran at 1.5MHz and my 8086 based H8 ran at 2MHz. Oh the ribbing they got for their “slow computer!” Lol! I upgraded the H8 with a Z80 and software programmable clock speed of 2 or 3MHz. No video or hard drives, just a vt100 terminal and dual 100K hard sector floppies. Could choose CP/M, HDOS, or UCSD Fortran operating systems. Had to write all of my own software and had assembly, Basic, Fortran and C languages to choose from. Great memories, thanks Ben!

@RogerBarraud

Жыл бұрын

The H8 was 8080A-based, not 8086.

@Q1745

Жыл бұрын

@@RogerBarraud my bad, yes 8080. I even tried to make sure I didn’t put 8086 when I posted. 🙄 Funny thing, I could use the C compiler available after the IBM 8086 based PC came out. About 95% success rate.

Ben the little triangle within the device block more usually means the pin is an edge triggered input.

Only Ben can make a 20 min video fly by as if it was a 2 min video

I remember dealing with all of these address locations when setting up hardware on pre-PCI, pre-Plug-And-Play PC clones, making sure you didn't have conflicts between your 16550A UARTs and your Adlib sound card and your whatever else. I had a solid _functional_ understanding at the time, but it's fascinating to learn what all of this stuff really meant. I would have loved for these videos to have been available to me back then.

@ivarnordlkken8082

Жыл бұрын

I had the same task when I hooked up 2 6821 to a Z80 via the edge-connector on an Amstrad computer.

I really appreciate Ben's teaching style of showing the simple or nieve solution first, and then diving into the more efficient and reliable solution. You get an idea of how the thing can work at a basic level, before showing you the limitations of that implementation and then showing the better way.

Excellent stuff. I kind of wish you'd left the mistake in place and tried to use the system though. I think there's a lot of value in that, for us to look at the weird behaviour and try to figure out what might be causing it, and to see how the process of debugging and troubleshooting this kind of thing works. I can imagine people getting one of your kits, hitting this kind of problem and then being totally stuck and discouraged because they haven't seen anyone successfully work through a situation like that

@iabervon

Жыл бұрын

Someone pranked Ben Eater by sending him a Big Endian UART, rather than the standard little endian kind? (Not really, since the status registers would also be backward, but it'd be so tempting to guess the serial data was configured backwards rather than all the parallel lines being wrong.)

Hi Ben. I have been a hobbyist for almost 50 years and a professional electronic engineer for almost 35. I have enjoyed your videos because they go right back to bare bones. I use MCUs these days but I wonder if I would be able to understand embedded issues as well as I do, if I had not been a professional learning through the era of MPUs and discrete peripherals. While I am loathe to make a criticism as small as this one is, I'd like to point out that it is not a good idea to tie two pins of a NAND or NOR gate together to realise an inverter. The reason is that the internal propagation time to each leg of the gate may vary in time, if only by pico-seconds. This can result in a glitch during transitions. Always best to tie one leg of a NAND gate high and use the other as the input to the inverter. That way there can be no race condition. Likewise, when doing the same with a NOR gate, tie one leg to ground and use the other leg as the input to your inverter. I watched your peripheral driver videos for the USB, the I2C & the SPI bus. Having written drivers myself, I felt you explained these very well. If you have have time perhaps you could try the 1-wire bus. I have never had the need to write a driver for these but there are still plenty of peripherals for these such as RTCs, memory devices and sensors such as the ubiquitous DS18S20 temperature sensor. Keep up the good work👍

@kvadratbitter

Жыл бұрын

A spurious high/low on the order of ps doesn’t matter in these asynchronous control lines working on chips with 10s of ns hold times on a 1 MHz system. There’s a much bigger timing issue if that’s a worry: some chip select line is direct from address line a15, some other has a 1 gate delay, and another has 2 gate delays. Also the clock signal distribution with different length signals creates a clock skew, perhaps on the order of ns. And of course the whole no-signal-return-path issue. Tying one input to high/low would lower power consumption for CMOS chips though. Ugh, I dislike how snarky I come across writing this, sorry.

I hooked up my 6551 to the 6522 chip to take advantage of the IRQ functionality. I've implemented my MAX3100 UART directly though. I understand using the WDC 6551 chip for teaching purposes but I highly recommend looking into other options.

Finally! Got my hardware working at 0x7000, however the software does not work - not even loopback. My friend and I are looking forward to see how you handle it. Thanks, Ben.

@daviddawkins

Жыл бұрын

For a moment there, was thinking...that's an expensive kit. I have only just woken up though

@aliceitc8380

Жыл бұрын

​@@daviddawkins me too I was really confused 💀

@MAYERMAKES

Жыл бұрын

​@@daviddawkins hah😂 same.

@starlii10

Жыл бұрын

It says on my app that this was posted 7 days ago, but the video was released 50 minutes ago... KZread is broken again. Yay.

@CraigNeth

Жыл бұрын

@@starlii10 He probably makes it available to Patreon members early.

I can't wait to watch this. I knew wayyyy too much about serial connections back in the day. Kermit, SLIP, SLIrP, making clamshell connectors and putting the pin in the wrong place... GOOD TIMES!

@RogerBarraud

Жыл бұрын

Null modems, guessing games around DCD, CTS, DTR, DSR... yup, fun and games 🙂

@PeterWillard

Жыл бұрын

@@RogerBarraud In my early work days, when everything was still RS232 versus Ethernet, I was the goto guy on-site when folks had trouble connecting device 'X' to device 'Y'. Lot of good that skill does me now... lol. Unless you are building a project like Ben's... and then it all comes back. Hmmm... Where is my HP4951C?

There is never enough Eater videos!! This series is awesome to see how everything’s built together.

I'd love to see how neatly you would solder all of these chips onto a perf board. Clearly your wire game is top notch.

back in the early 80's when my main computer was a TRS80-M1 I got into BBS's and used my cassette port to talk to the modem without a UART. I remember writing my own version of the terminal program (wanted to support more vt100 type codes than the Tandy one did) and it was very eye opening about how tight the timing had to be, and this was for the much slower 300 baud speed, which gave me 'nearly' but not quite enough time to refresh the screen. Figuring a way to scroll the screen in a 'multitasking' manner when you didn't have enough time to move the 1024 bytes that made of up the memory mapped screen, in the 1/300 of a second available. Finding the tech specs on the exact clock ticks each instruction required was a critical part of that project.

Direct Memory Access is such a big word now for gaming but it probably was so common on these kinds of systems, wow.

@gower1973

Жыл бұрын

I think DMA became a thing in the 16bit era, not 8bit systems like this

@falksweden

Жыл бұрын

DMA was a big thing with the Amiga in the 80's

@Stingpie

Жыл бұрын

you kinda got this backwards. DMA was uncommon for cheap microcomputers in the 80's, and nowadays, pretty much every single CPU comes with DMA.

@clonkex

Жыл бұрын

DMA isn't Microsoft's DirectStorage API (which is the thing gamers care about), but perhaps DirectStorage makes use of some form of DMA.

@bobbyaremyshoes2233

Жыл бұрын

@@gower1973 8bit Gameboy Classic had DMA to transfer sprite data. But this console was released rather late, in 1989

Wish we had this instructional videos when I was playing with my Commodore 64. I got into industrial control in school and PLCs. Which was a good career but never really understood the component level stuff as far as processing goes. Thanks Ben for helping me understand.

I always appreciate the little mistakes that are left in, and showing the fixes. Your videos are wonderfully soothing and informative, like Mr. Rogers or Bob Ross teaching electronics.

Amazing how many ways there are to notate active low signals... I've never encountered the B but quite often one that you didn't mention: a lower-case n after the signal (like CSn). For "negative", I presume. Also, I think that the triangle that you mention denotes a clock input, or maybe generally any edge-triggered input.

@RogerBarraud

Жыл бұрын

'n' is usually a prefix. There's also the '*' convention (usually a suffix IIRC). I usually use the n-prefix for my own stuff... it preloads my mind with the idea that the following thing is inverted... rather than modifying something that I first read as uninverted 🙂 YMMV...

I love these videos. My breadboard routing never looks as good as yours.

If only I could obtain the different WDC chips locally in South Africa.... With a non-functional post office, importing them are SO expensive via courier services. Great video as usual, thank you Ben.

Amazing content as always! Thank you!

I was really looking forward to this! Thank you!

Thank you so much for clear and valuable lessons.

You could of course prevent the 7000-7FFF address waste by checking the two conflicting bits with an AND gate, if it returns 1 you disable both the VIA and the UART to enable another device you may later add into that address space to be enabled on its own.

YES!! Thank you so much, Ben. I have learned so much about computers through your series, things i just could not wrap my head around before now make perfect sense. Looks like we have a new 65c peripheral chip to play with, I had a nightmare getting the 65c02 and 65c22 in WDC form, had to get rockwell versions instead from ebay.

@YateyTileEditor

Жыл бұрын

I've always found them to a be available on Mouser. Hopefully I wasn't just lucky but they've always been in stock when I checked.

Not to forget the small 'n' prepended to a pin name also being used for active low pins :)

With this amount of devices, I would do this: as you described in a previous video, use an eeprom as a logic gate. Input all address lines into the eeprom, and the output data lines all function as chipselect lines for all of your devices. This will scale a little better, and will also prevent situations in which multiple devices are fighting over the bus!

See guys, just when you thought it was difficult. Now all we need is to get Ben to take a look at our respective economies. This channel is pure paracetamol.

This takes me back to my computer engineering grad school days back in the early 90's. Good times.

Its great seeing you upload again

If you've posted it tomorrow, would it be Ben Easter?

@desertfish74

Жыл бұрын

Thanks for the chuckle

Yes ben keep us mesmerised thank u

They also used to use an asterisk for active low indication.

New videos from Sharman and Eater on the same day, wow! Ben looks too young to remember things like the Western Digital WD1402 or Intersil IM6402 - and should account himself thankful! (Using those was a little squirrely - but certainly beat tweaking trimmers for the LC-controlled receivers and transmitters that preceded them! I remember the Western ad in places like Scientific American: "We uncoiled the data transceiver!" (No inductors in their design...) I did a software UART on one of the smaller Atmel devices not too long ago (short on I/O pins and board space), but simplified things some by using a 9.216 MHz crystal so that the CPU clock divided down nicely to the bit rate. (Still a PITA.) The PIC didn't need to be doing anything else when it was exchanging data, which were just 18-byte messages, so they were pretty quick. (Should probably just have put a CPU core and a UART on a FPGA)

@michmart9261

Жыл бұрын

Who's Sharman may I ask?

@sirnukesalot24

Жыл бұрын

James Sharman runs a similar channel where he's been building an 8-bit pipelined CPU from scratch. He also uses surface-mount components on in-home designed PCBs. Ben gets you to where you understand it, James runs the advanced class.

@ciano5475

Жыл бұрын

@@sirnukesalot24 Also check out FoxTech and his 486 Breadboard Computer.

@sirnukesalot24

Жыл бұрын

@@ciano5475 Yeah, I saw that. I'm already following FoxTech just like you are. I think most of us knew he was going to need that fourth bus transceiver no matter what.

It's odd - technical but therapeutic, could listen for hours. Lyrical bytes

I once had a USB port on my laptop stop working; I think it was because of a serial killer...

@ke9tv

Жыл бұрын

And my wife passed me my breakfast through the pass-through over the kitchen counter. It was a cereal port.

@ivarnordlkken8082

Жыл бұрын

@@ke9tv LOL!!!

I was just seeing when you last uploaded and I was like "shit it is only a couple of weeks so he is not uploading anytime soon" but here you are spoiling us with frequent uploads

Great video

Fascinating!

This type of videos need extreme research. Keep it up ben ❤

I like your videos a lot. It's my zen moment of attention.

The 6551 appears to be easy to use, but they were made by multiple vendors and each version has different requirements to the clock circuit and often those do matter. Feeding it with an external oscillator resolves that. Its timing requirements are easy to meet when driving it with a 6502, but trying to use a different CPU may be difficult and trigger weird bugs, like a stuck transmitter ready bit. Interestingly it is always stuck for the W65C51N and even documented as such.

Would it make sense to use a 74ls138 now that the address decoding is getting more complex?

It's a pity that this channel uploads so few videos, they are of great quality I love them

Absolutely perfect timing. I just got the MAX232 chip in yesterday, and was about figure out the the uart on my own today. Super excited.

Finally new video love your vids

Thanks

Great stuff as usual. I cant figure out when the video was posted but looks like recently from the comments. What comes next? Connecting monitor and keyboard?

Thanks Again !

You are amazing!

Fantastic

I never really fully understand your videos but i try my best to rewatch it until I do

I had to work on a microcontroller that we had to "bit bang" serial comms... you're right, it's very touchy.

Great video! The talk about bus arbitration got me thinking: is there a chip that basically halts the 6502 for a couple cycles while other chips request/write to the RAM? Or maybe something can be done with interrupts and a few gates? 🤔 I'm likely missing some edge case that complicates this, but it sounds fairly simple in principle

@wbfaulk

Жыл бұрын

The 6502 has a Bus Enable pin, which, when low, causes the 6502 to set its address and data buffers and the read/write pin to high impedance.

@chitlitlah

Жыл бұрын

The Atari 8-bit computers function along those lines, with the Pokey chip (mainly responsible for video) halting the 6502 when it needs to read memory. That's why you can't reliably judge time by processor cycles unless you disable Pokey (giving you a blank screen).

I needed this 3 to 4 years ago, I struggled so much to make something work with uart and rs232

the day ben eater uploads a video is a happy day

A great video and very instructive. I have some of the original 6502 books from Sybex. Quick question - the schematics (on the website) have SB140 diodes on the IRQ lines, are these needed?

That mistake in the wiring you caught... Heh. A while ago I mounted a rpi in a cabinet that contained contactors, sometimes when they switched they generated an rf pulse big enough that the rpi would detect it and include it as an input. The damn thing worked fine on my desk, in the cabinet... It went haywire. Eventually rather than trying to add shielding or any of that and since the pulsed were so short in duration I just modified the code not to accept inputs that happened faster than a certain time frame. Biggest head scratcher I've had for a while.

@melkiorwiseman5234

Жыл бұрын

I bought a daisy-wheel printer for a "parts" price because it was continually "blowing" an on-board fuse. I took the fuse wires out to an external fuse holder and began experimenting. After a while, I realised that it was blowing the fuse whenever the AC powered cooling fan switched off after cooling down the print head following a long session of printing. I added a mains-rated 0.01 microfarad capacitor across the fan and suddenly there wasn't a problem. Sold the printer later for a huge profit.

"RS232 interface with the 6551 UART" ah yes, those truly sound like some symbols I'd enjoy!

Hey Ben, love the video, built my own computer based on your videos! Are you planning a video on I2C? Would be very interested in that!

Great episode! I like the parallels that can be made between your simple addressing circuit and the disjointed address blocks it creates, to the same type of addressing when eg programming for NES! (it is a 6502 as well after all, haha) At 20:40 we can see your bus wiring is indeed getting untidy and hard to make sense of (even for you!), perhaps it's time you use the amazing trick with power-rails-as-bus you showed us for your computer-from-scratch series?

You ever plan on covering HDMI? BTW love your content!

WoW another Ben Eater's magic uploaded

Hello there! I really appreciate the content you post as a embedded systems grad student, it would be helpful, if you can get some videos on communication protocols!

excited for a new ben eater video

Hurray! It's a new video

He is a legend.

Considering how well suited the keyboard protocol seems for RS232 I find it kinda odd that there seem to have been almost no keyboards with an ordinary DB9 serial port, even though there where lots of serial mice back in the day. PC keyboards always seem to have used a DIN or mini DIN connector until everything became USB. Why is that?

@rwsrwsrwt

Жыл бұрын

Maybe, it's because computers may have more than only one "ordinary" serial port and they wanted to make sure the keyboard is connected to a specific port (using a connector that doesn't fit anywhere else). That makes it easier for the BIOS to handle keyboard inputs (especially back when memory - including ROM - was expensive and you'd hard-code things like that rather than wasting memory just to detect what physical port the keyboard is connected to). The DB9 interface also doesn't offer a supply voltage to power anything connected to it. Having a separate power cable (in addition to the data cable) to supply the keyboard or just drawing current via the (unused) signal pins (what serial mice usually do) isn't a nice solution either. Early PCs didn't come with a mouse and weren't "designed" with a mouse in mind. A serial mouse came later as a "cheap" solution you could add to something you already had. But there were also mice that came with expansion cards to be installed into the PC.

Ben's new video out, get the popcorn out. What.. only 22mins? :(

Ben Eater uploads at the same time as James Sharman? Today is my lucky day

Ben NEEDS to add an NTSC or PAL TV signal for this!

It's a small thing, but thank you so much for referring to address 0x5000 hex as "five zero zero zero", not "five thousand"! That bugs me so much with other videos, since "thousand" is a specific amount and that's more like *twenty* thousand. I never have the heart to correct people about it though, so i'm just glad whenever someone says it correctly!

@kvadratbitter

Жыл бұрын

What’s incorrect about saying five thousand? What do you mean by “amount”, how is that relevant in this case?

The best thing when I see ben uploading

Awesome

Wake up babe new Ben Eater video dropped

Ben Eater rules!!!

Ben, did you actually notice the cabling mistake [D0..D7] when you intended to bend the cables and felt they did not bend correctly? Like muscle memory triggered you into checking the order of the connections? It certainly looks this way when watching this (yet again) excellent video of yours.

Quick question what, keyboard are you using it sounds amazing.

What about a 74HC138 for I/O address decoding? This its help even the LCD display could be connected to the data bus directry. And just a warning: The /SO input of the 6502 shouldn't be left floating or the overflow flag could be set randomly in the P register.

This is great. But at this point maybe a decoder for the 4 most significant bits would be the way to go

Dear. thanks for the video.... may I ask what schematic tool you are using to draw those diagrams?

yay new video!!!

Question; is it worth using a 2-to-4 or a 4-to-16 logic IC for address decoding? I ask because they're hard logic, so they're fast, and easy to explain as an array of gates, and would do all the selecting all the peripherals need. (the 74LS154 comes to mind, I'm sure there's an F or HC version as well)

@YateyTileEditor

Жыл бұрын

Absolutely! I use 74xx138 s 3-to-8 selectors because they're cheap, ubiquitous and a pair can be turned into a 4-to-16 selector with no extra ICs if needed.

If you have lots of different IO ports what about using a small eprom to decode? I always planned and wanted to build my own computer (probably a Z80) but so many projects and so little time. So watching you doing it (and others) is the next best thing. Really enjoy your videos

@ke9tv

Жыл бұрын

No need for an EPROM - address decode is pretty simple. Ben just didn't want to spend the board space on a demux and address comparator. In the old-school TTL he's working with, it's still just a 2-package solution.

@ke9tv

Жыл бұрын

@@jayneatkinson2747 Yeah. The people who try to replicate 1970s minicomputers with modern IC's tend to overlook that, but the DEC, Data General and Wang machines all had PALs (no GAL's yet!) here and there. Of course, the simple GALs are all going obsolete fast. I probably need to get tooled up sooner or later on the bigger CPLD's even though they seem like total overkill.

@kvadratbitter

Жыл бұрын

A single ‘138 would be faster and use less board space than the current NAND solution, without adding any complexity IMHO.

I like how simple it it to do the memory decoding, in the Z80 is a bit harder but it has the advantage that it activates two control signals, one to access memory and one to access IO, In my case for the memory decoding I use a 74HC139

@melkiorwiseman5234

Жыл бұрын

The Z80 has the small advantage that you have 256 I/O ports on top of the 64K memory addresses and they don't share the same memory space. An undocumented feature of all Z80 CPUs (so far as I know it's all of them) means that you can also access up to 64K I/O addresses instead of only 256. The instruction OUT (C), A functions as OUT (BC), A which means that if you load a 16-bit address into the BC register pair and then use the OUT (C), A instruction, it will put the full 16 bits from the B and C registers out on the address bus. The same for the IN A, (C) instruction. Most hardware engineers never took advantage of this feature, either because they didn't know about it or because it was undocumented and they feared it might not be supported in some versions of the Z80.

@MrWilliam932

Жыл бұрын

@@melkiorwiseman5234 Yeah I was aware of this, wich is great, but I don't know why they didn't directly say in the datasheet that user could access 64K IO addresses.

1:10 instead of using a nop instruction loop for a delay, could you have used a timer interrupt? I’m not very informed about neither the arduino, nor 6502 software/hardware. I think the 6502 is very similar to the 68hc11 and s12 controller families that I learned about in engineering school.

It's actually a vibe whenever you post a new video 😂

This are great video's

Such nostalgia. I had to write a UART controller for an embedded system, long, long ago.

Hooking my brain up to that would get me fried More seriously we need to discover the max232 max233 max2323 chips and limitations in the next video and hooking up non voltage tolerant devices to rs232

@ben would you please recommend a course / uni I can attend to get half as smart as you in digital electronics? Second thoughts, I will become a patron and do your courses first, this is likely all the training I will need/want.... :) Brilliant content!

I like where this is going! 😁

This is basically a simpler, larger version of s modern microcontroller. That's very neat.

Wouldn't a simple binary decoder, like an LS138 make that address selection a lot easier? Put the 3 MSB of the address bus into such a decoder and you have 8 'chip select' outputs that you could combine to select ram/rom/vif/uart/ .... other? I mean I know you started with just basic ram/rom and a simple pair of nand gates, but ripping those out for a single decoder would seem warranted at this point. And even more expansion possible.

@sashimanu

Жыл бұрын

Absolutely! A 74whatever138 will do, along with some diodes for address space bridging if needed.

@paulheitkemper1559

Жыл бұрын

That's what I thought as well, but he mentioned something about timing. So I figured he cascaded those NAND gates for that reason. It gives time for the first chip to transition into high impedance before the next chip activates.

@ivarnordlkken8082

Жыл бұрын

@@paulheitkemper1559 Yes, there are more levels of gates in a universal decoder, like 74138 or 74238. I think it's 4 levels. I have to check the datasheet first to be sure. So it takes longer time for the signal to appear on the output. I used it successfully on a Z80 at 1 MHz.

@johnm2012

Жыл бұрын

A '138 is very useful for address decoding but you can't get much simpler than three NAND gates.

@eDoc2020

Жыл бұрын

That would bring more tradeoffs, namely reduced address space for the memory unless you add extra layers of decoding. The 65xx series chips are designed to be addressed directly using the address bits so unless you are using other chip families or need more than 8 interface chips it doesn't make much sense to use more advanced decoding.

Love the series, starting to experiment again because of it! Question: Prolific or FTDI chipset for the USB to RS232 cable, which is 'best'? USB to UART cables are also abundant, 5v, 3.3v and other options. What brands/types are most reliable for using on a Win10/11 machine? My PCIe to breadboard adapter probably ain't coming so aiming for second best :)

@doctorbobstone

Жыл бұрын

I'm not familiar with the Prolific chip, but I've seen the FTDI chips get used a lot, both professionally and by hobbyists, so for me, it would be the default answer unless there was something special about the Prolific chip I needed. YMMV, of course.

@rafalklepinski7372

Жыл бұрын

@@doctorbobstone Prolific PL2303 is, as the name might imply, everywhere and cheap, which isn't always the right choice. Amazon and my local computer shop carry them in abundance. I'm kind of leaning in the USB to UART direction, but for this particular project that's cheating :) Nonetheless having the UART 'taken care of' inside the adapter would ease design a smidge.

@doctorbobstone

Жыл бұрын

@@rafalklepinski7372 the fact that you consider it cheating makes me unsure of I understand what you're planning. I assumed you are talking about using an FTDI or Prolific chip/cable with the USB of your host computer to talk to your 6502 computer using serial. I don't see how that's cheating, hence my confusion... 😁 Anyway, if you've got a reason to use one or the other, go for it. I've just used FTDI cables a lot and seen EEs chose them for use in their designs and places like Adafruit selling them, and so on. Those are just data points, though. You might not find them relevant for your use case.

@rafalklepinski7372

Жыл бұрын

@@doctorbobstone Cheating in the sense that the UART is already built into the adapted and outputting TTL voltages, presumably skipping adding the UART chip in the video :) Also now that I read comments down below about the various silicon bugs in the UART used in the video I'm skeptical of using it. In the future might use the UART version to send data from PC to discrete cmos combinational logic circuits to make calculations and return results to PC.

@johnm2012

Жыл бұрын

​@@rafalklepinski7372 Unless I've completely misunderstood what you're talking about you still need the ACIA or UART chip on the breadboard. The TTL levels used by the FTDI USB cables connect directly to the Tx and Rx pins of the 6551, bypassing the MAX232 charge pump chip.

After watching at first I though, aren't IRQ lines open-drain and can be connected to single wire? But later I saw that W65C22 has N and S variants. Are you going to solve it using schottky diode or AND gate?

@eDoc2020

Жыл бұрын

Another possibility if you don't want to AND the lines is hooking the ACIA's IRQ line to a pin of the VIA.

Hi, any idea why the data being received by the 6551 UART is incorrect? I've checked whether the baud rate, parity, and data bit settings match on both devices. Thanks in advance.

As shown @15:53, the decoding logic does not prevent a conflict between the ACIA and the VIA when the high 4 bits are [0111]. A better address decoding scheme would have been to use [010x] for the ACIA, preventing this bus conflict. Sure, you wouldn't normally address the conflict range, but why allow an errant software glitch to cause a hardware conflict when you don't need to? LOL - I paused literally seconds before you covered it.

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