Search found 485 matches

by guesser
Thu Oct 15, 2020 7:43 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 442
Views: 14749

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

I've been preoccupied with preparing various bits of teletext stuff for the upcoming virtual block party event, which is why I've not made any progress on the vectorising for a while (also getting ill :( ).
Hopefully I can give it some attention again next month.
by guesser
Thu Oct 08, 2020 11:20 am
Forum: off-topic
Topic: Acorn Art Thread
Replies: 1497
Views: 123845

Re: Acorn Art Thread

FourthStone wrote:
Thu Oct 08, 2020 9:36 am
would be interesting to see what could be done with more frames thrown in.
More frames you say? :D
output.gif
output.gif (714.32 KiB) Viewed 242 times
Created using https://8bitkick.github.io/teletext-express/ and tweaked a bit before converting to a teletext signal
by guesser
Mon Oct 05, 2020 9:11 am
Forum: off-topic
Topic: Acorn Art Thread
Replies: 1497
Views: 123845

Re: Acorn Art Thread

Let’s see some art from you all. Anything. Just have a go. Indeed, and if I could add, the teletext community are doing Blocktober all month, with submissions open on the Chunkytext teletext service via https://blockparty.zxnet.co.uk Everyone's welcome, especially beginners! :D Here's one I made ea...
by guesser
Sun Sep 27, 2020 1:31 pm
Forum: 8-bit acorn hardware
Topic: 6522 differences?
Replies: 10
Views: 289

Re: 6522 differences?

Fair dos. Just woke up and didn't parse the sarcasm correctly.
by guesser
Sun Sep 27, 2020 12:25 pm
Forum: 8-bit acorn hardware
Topic: 6522 differences?
Replies: 10
Views: 289

Re: 6522 differences?

Colday wrote:
Sun Sep 27, 2020 9:34 am
Unless it's just to relabel the dross into something useful saleable. That works right?
The goal is to obtain money, not to provide useful parts.
by guesser
Sun Sep 27, 2020 2:17 am
Forum: 8-bit acorn hardware
Topic: RCA for UHF, bayonet for composite ... wtf?
Replies: 9
Views: 367

Re: RCA for UHF, bayonet for composite ... wtf?

This is one of those annoying things where 10 items are only a little more than 1 item... and why I have boxes of crap as a result :-) eg https://www.amazon.com/ZOSI-Female-Connector-Adapter-Security/dp/B072ML5ZH2 I only have two. When I'm not using the beeb they live on opposite ends of a BNC-BNC ...
by guesser
Sun Sep 27, 2020 1:55 am
Forum: 8-bit acorn hardware
Topic: RCA for UHF, bayonet for composite ... wtf?
Replies: 9
Views: 367

Re: RCA for UHF, bayonet for composite ... wtf?

I use a BNC to phono adapter and a standard phono patch cable, though I do have a BNC cable I mutilated in a box somewhere I think.
by guesser
Fri Sep 25, 2020 8:43 pm
Forum: 8-bit acorn hardware
Topic: RCA for UHF, bayonet for composite ... wtf?
Replies: 9
Views: 367

Re: RCA for UHF, bayonet for composite ... wtf?

The one teeth-gnashing annoyance is the serial port. While I can see the attraction of avoiding a DB25, and the DE9 connector wasn't commonplace until several years after the BBC was designed, they really could have chosen something that wasn't rotationally symetrical. Having a rotationally symmetr...
by guesser
Mon Sep 21, 2020 11:41 am
Forum: programming
Topic: BMP to Teletext
Replies: 7
Views: 393

Re: BMP to Teletext

FourthStone wrote:
Mon Sep 21, 2020 2:52 am
Thanks for the quick response, will look over Kieran's code and I am very interested to see your code when released :D
It's not mine, I've just been following it too, eager to hack it around and do silly things with it once it's ready :)
by guesser
Mon Sep 21, 2020 2:20 am
Forum: programming
Topic: BMP to Teletext
Replies: 7
Views: 393

Re: BMP to Teletext

If you're patient that one will be released and you can look at the code :)

There's also Kieran's image2mode7 which does colour.
by guesser
Sun Sep 20, 2020 5:50 pm
Forum: 8-bit acorn software: other
Topic: BBC Basic Bot (on twitter)
Replies: 25
Views: 2145

Re: BBC Basic Bot (on twitter)

Recently they've also been working on a video-to-MODE7 conversion tool. I wrote a script to turn the exported screens into a teletext signal and fed it into my Acorn Teletext Adapter. 10fps test https://twitter.com/ZXGuesser/status/1306196124437557248 25fps test https://twitter.com/ZXGuesser/status/...
by guesser
Sun Sep 20, 2020 12:30 pm
Forum: other events + general event chat
Topic: Blocktober virtual teletext block party 24th & 25th October
Replies: 0
Views: 87

Blocktober virtual teletext block party 24th & 25th October

On the basis of our April Blockdown event not being a complete shambles, we're doing another virtual teletext block party in October. :)
https://www.arbitraryfiles.com/events/bt20/index.html
by guesser
Tue Sep 15, 2020 11:25 am
Forum: general
Topic: Shout out to Batronix customer support
Replies: 1
Views: 133

Re: Shout out to Batronix customer support

They are good. I pointed out that following an update prog express was trying to write settings to the All Users application data directory instead of the account running it and they fixed it in the next point release iirc. This was back on XP where I guess most people were still running everything ...
by guesser
Sat Sep 12, 2020 10:21 am
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 442
Views: 14749

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

I believe the first left column is 111x1xxx rather than 111xxxxx.
by guesser
Thu Sep 10, 2020 5:06 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 442
Views: 14749

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

If you look at the PLA Dump in the document, you can see the inputs transcribed in a form which makes it easy to see how they match opcodes, "x"s for bits where we don't care. This allows us to easily determine the smallest ranges of values which must correspond to opcodes in a single family, and t...
by guesser
Thu Sep 10, 2020 12:37 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 442
Views: 14749

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

Yes - in as much as we can determine the smallest blocks of opcodes which the PLA handles in the same way, and presume them to be small variants of the same thing. For example, we can see that there's a signal which is fired for $0x, and nothing more specific than that, therefore all opcodes from $...
by guesser
Thu Sep 10, 2020 11:37 am
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 442
Views: 14749

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

The inputs to the narrow ROM are what I'm calling the 2-bit ID - the high two output bits are just the top two bits of the 10-bit output address; nothing remarkable about them as far as I know (unless you know differently!). That's what I thought, ta. So those extra two input bits should be explain...
by guesser
Thu Sep 10, 2020 11:26 am
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 442
Views: 14749

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

What are you calling the 2-bit id? The extra two inputs to the narrow ROM (jump table?), or the high two output bits?

I've not kept up with what names you're using for different parts sorry.
by guesser
Thu Sep 10, 2020 2:00 am
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 442
Views: 14749

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

It's because I marked up the transistors to ground as 0s and the lack of a transistor as a 1 (which we determined later was reversed). I realised too late how counter-intuitive that was, and it caused a lot of errors, most of which I caught a split second after writing the digit and had to undo and ...
by guesser
Thu Sep 10, 2020 1:52 am
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 442
Views: 14749

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

Yep, those are all stupid transcription errors on my part that I made when marking up the drawing.
by guesser
Thu Sep 10, 2020 12:46 am
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 442
Views: 14749

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

Unfortunately I still have to go through the ROM by hand and manually mark each bit with a coloured square. This isn't some image processing magic. :( But at least this way, the final step of converting to hex is automated. However, your timing is good, because I have just a few minutes ago complet...
by guesser
Thu Sep 10, 2020 12:35 am
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 442
Views: 14749

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

Do you think you could run this process through the best photos we currently have of the 8271 and get a new dump of the ROM (as we've found a few transcription errors here and there, but there may be more). Have you got a list of places you suspect errors? My transcription of the ROMs were done bef...
by guesser
Mon Sep 07, 2020 1:48 am
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 442
Views: 14749

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

I've traced back the input bits 8 and 9 to the small ROM decoder and they're are related to rows 0 and 1 of these decode tables.

I'll need to trace out a bunch of the logic below the left table to see what actually controls them to see which columns activate them and how. :)
by guesser
Sun Sep 06, 2020 8:41 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 442
Views: 14749

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

Yes I believe those are pull ups, to the big Vcc off the top of the screen, hidden under the ground metal but with no connection to it. I recognise where that is :)
by guesser
Sun Sep 06, 2020 6:18 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 442
Views: 14749

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

Oh, now I understand it I think! The two inputs at the top are latching the value from the bus when switched on and off in the correct sequence. The first one to let the bit in, and the second one holds it in (holds it low when the bus pulls up again) The bottom input makes sure that no columns are ...
by guesser
Sun Sep 06, 2020 5:55 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 442
Views: 14749

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

Precharge and discharge in the sense of it being a dynamic circuit? If so that would explain why my DC analysis with no thought given to capacitance made no sense.
by guesser
Sun Sep 06, 2020 2:02 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 442
Views: 14749

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

I couldn't figure out the logic of the top pair of inputs as it seemed more complicated than just enabling/disabling the whole thing. The lower input apparently pulling down both column lines at the same time as turning on the pull up for all the rows puzzles me too. There's obviously something I'm ...
by guesser
Sun Sep 06, 2020 12:41 am
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 442
Views: 14749

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

Is there any hope of tracing the opcode bits through the PLA so see which opcode bit combinations activate what? Even identifying just a few critical opcodes could be enough to cause a cascade of successful opcode inference. Eventually! I keep picking away at it like a scab, but there's a whole lot...
by guesser
Sat Sep 05, 2020 11:26 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 442
Views: 14749

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

I'm not having any real difficulty vectorising from the existing photos. Between the two chips I'm managing to identify what goes where.
by guesser
Wed Sep 02, 2020 1:09 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 442
Views: 14749

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

I thought the suggestion was four of the bits coming off the bus into the address decoder are from the case register and four from a segment address generator whatever those are. With the last two bits (page?) coming from somewhere else. Vague I know! :)

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