Search found 136 matches

by cmjones01
Wed Dec 27, 2017 12:49 pm
Forum: hardware
Topic: Playing with the SAA5050
Replies: 14
Views: 1169

Re: Playing with the SAA5050

Nice job, getting the SAA5050 working like that. Having seen the post on Facebook, I dug out my old Mullard data books and have found a more recent datasheet for the SAA5020, dated 1981. I 'scanned' it (photographed the pages with my phone and pasted the results together into a slightly shonky PDF, ...
by cmjones01
Sun Nov 26, 2017 5:09 pm
Forum: introduce yourself
Topic: Hi from Peterborough, CAMBS
Replies: 14
Views: 835

Re: Hi from Peterborough, CAMBS

There's just one anomaly - when you power it on the first time, it does the expected POST beeps. If you turn it off and on again with less than 1 minute pause, the first low beep is overlayed with a higher frequency beep - sometimes higher than the second beep. That's normal. The sound before the p...
by cmjones01
Fri Nov 24, 2017 10:24 pm
Forum: hardware
Topic: Acorn Teletext adapter on B+
Replies: 15
Views: 618

Re: Acorn Teletext adapter on B+

A quick update on this one: I got my Morley teletext adapter running and that works fine with the Raspberry Pi. It uses a newer chipset that does all the page capture and decoding in hardware so the Beeb's job is easier. Having thought about it a bit more, I have a theory as to why the Acorn adapter...
by cmjones01
Tue Nov 21, 2017 2:15 pm
Forum: hardware
Topic: Acorn Teletext adapter on B+
Replies: 15
Views: 618

Re: Acorn Teletext adapter on B+

guesser wrote:What tuner does the Acorn have? I found mine in a databook on archive.org https://archive.org/details/MullardBook ... Tuners1987
It's a Mullard U341 (Philips 12NC part number looks like 2122 127 41491 but the label's a bit scuffed).
by cmjones01
Tue Nov 21, 2017 1:51 pm
Forum: hardware
Topic: Acorn Teletext adapter on B+
Replies: 15
Views: 618

Re: Acorn Teletext adapter on B+

guesser wrote:
cmjones01 wrote: The later Acorn/GIS decoder uses a later chipset which does the decoding in hardware, like the Morley one. Actually, I've got a Morley adapter I should try out too.
Yeah, that's the one I was thinking of. I believe it interfaces with the teletext IC using I²C?
That's the job, yes.
by cmjones01
Tue Nov 21, 2017 1:51 pm
Forum: hardware
Topic: Acorn Teletext adapter on B+
Replies: 15
Views: 618

Re: Acorn Teletext adapter on B+

It has the same TDA2541 and things on the tuner board. Is the SAW filter a RW153A? Will be interesting to compare RF circuits, I expect both to be very similar to the datasheet reference design :) The SAW filter is an SW153A in my Acorn adapter, driven by an SL1430. There's a handy link, LK3, which...
by cmjones01
Tue Nov 21, 2017 1:36 pm
Forum: hardware
Topic: Acorn Teletext adapter on B+
Replies: 15
Views: 618

Re: Acorn Teletext adapter on B+

Completely different really, the Acorn one is as you say like a TV teletext decoder and the beeb just grabs the page data from it. While I've not probed out all the logic side of things yet so can't say when and how often signals occur, the speccy one stores incoming teletext packets into a 1kB SRA...
by cmjones01
Tue Nov 21, 2017 1:23 pm
Forum: hardware
Topic: Acorn Teletext adapter on B+
Replies: 15
Views: 618

Re: Acorn Teletext adapter on B+

aha! I should have thought of that, I have exactly the same issue with the Volex adapter for the ZX Spectrum that I'm currently reverse engineering :lol: Ooh, interesting. I wonder how similar it is to the Acorn one? The Acorn one basically loads each line of teletext data raw into an internal 1K R...
by cmjones01
Tue Nov 21, 2017 1:05 pm
Forum: hardware
Topic: Acorn Teletext adapter on B+
Replies: 15
Views: 618

Re: Acorn Teletext adapter on B+

guesser wrote:I assume you mean the Beeb getting stuck after receiving the first header? Not that it's always that time for every test.
It's more strange than that - the Beeb isn't stuck, the time at top right updates continuously, and I get occasional flickers of the rest of the page.
by cmjones01
Tue Nov 21, 2017 1:04 pm
Forum: hardware
Topic: Acorn Teletext adapter on B+
Replies: 15
Views: 618

Re: Acorn Teletext adapter on B+

I know it's bad manners to reply to one's own posts, bu I had a brainwave. Though the Acorn Teletext adapter and ATS seem to be designed to handle 16 lines of teletext information, I wondered if that in practice they couldn't. I edited the source to the Raspberry Pi's teletext program (reducing HEIG...
by cmjones01
Tue Nov 21, 2017 12:24 pm
Forum: hardware
Topic: Acorn Teletext adapter on B+
Replies: 15
Views: 618

Acorn Teletext adapter on B+

Does anyone here have experience using the Acorn Teletext Adapter on a BBC B+? I am hoping to set up a teletext display in my office using vbit2 and teletext on a Raspberry Pi. I've got everything set up and it almost works but not quite. IMG_20171121_131753.jpg There's a good teletext output from t...
by cmjones01
Mon Nov 20, 2017 2:34 pm
Forum: off-topic
Topic: Work experience BITD - claims to fame, and infamy
Replies: 15
Views: 1167

Re: Work experience BITD - claims to fame, and infamy

It's ages since I've logged in here, and I only came to look up some Teletext stuff, but this thread caught my eye. Regarding work experience, I went to school in Cambridge, just round the corner from the Acorn offices, and there seemed to be a long-standing relationship with the company: there was ...
by cmjones01
Thu May 18, 2017 12:50 pm
Forum: software: other
Topic: Anyone got Communicator system software? (Basic has 65816 assembler)
Replies: 70
Views: 5594

Re: Anyone got Communicator system software? (Basic has 65816 assembler)

Back on topic (sort of): the page on Chris's Acorns speculates that the ULA in the Communicator could be the same as the one from the Electron but, looking at z0m8ied0g's Acorn Communicator - Dialling ViewData BBS video, it looks like it's using MODE 7 to display Viewdata. So, was the ULA in the Co...
by cmjones01
Fri Apr 28, 2017 6:49 am
Forum: hardware
Topic: Why so few off-shelf All in one video ICS (ie 6847, Tms9918 descendants
Replies: 17
Views: 1328

Re: Why so few off-shelf All in one video ICS (ie 6847, Tms9918 descendants

Interestingly, a 6545 video controller also exists, though I think it's a later product. I have a piece of equipment which uses one, though its CPUs (multiple) are 80186s!

Chris
by cmjones01
Sun Apr 09, 2017 4:12 pm
Forum: other vintage computer hardware, software and games
Topic: Superbrain power supplyhi
Replies: 53
Views: 2533

Re: Superbrain power supplyhi

I'd say that the PSU is almost certainly OK. In a simple flyback design like that one where only one rail is regulated, the secondary outputs (like +21V) won't be able to deliver their rated current until there's enough load on the main output (+5V here). I'm guessing the monitor is powered from +21...
by cmjones01
Mon Mar 27, 2017 12:10 pm
Forum: hardware
Topic: Faulty BBC B
Replies: 17
Views: 1098

Re: Faulty BBC B

A simple thing to check is the power supply connections to the motherboard. They're push-on tags which suffer from corrosion and loose connections, causing symptoms just like you describe. I had this on my model B, and tightening the wires to the right hand side of the board near the RAM fixed the p...
by cmjones01
Tue Feb 28, 2017 9:05 am
Forum: off-topic
Topic: potential differens between two elec things
Replies: 8
Views: 575

Re: potential differens between two elec things

Unless one of the devices actually has a serious wiring fault, you almost certainly don't need to worry about this. It's absolutely normal for consumer electronics, like TVs, VCRs and so on, which have 2-wire mains cables, to 'appear' to have about half the mains voltage (so, around 120VAC) on the '...
by cmjones01
Thu Feb 23, 2017 4:33 pm
Forum: emulators
Topic: how to get rom in beebem ?
Replies: 14
Views: 1509

Re: how to get rom in beebem ?

The standard model B doesn't come with an SRLOAD command, or indeed any other sideways RAM utilities. Traditionally they'd be supplied in a ROM or on disc. However, you can get an SRLOAD command by using one of the 'upgraded' hardware configurations in Beebem. The 'BBC Model B + Integra-B' and 'BBC ...
by cmjones01
Mon Jan 16, 2017 9:01 pm
Forum: hardware
Topic: A request for rare 32016 based hardware
Replies: 48
Views: 3205

Re: A request for rare 32016 based hardware

Very curious that the clocksp results differ. I ran the test a couple of times and got the same results. Meanwhile. I've run 'pi' under Panos, having set the date as advised above. The results are: 100 digits 0.2900 1000 digits 23.1400 3000 digits 204.1600 I suspect the final two '0' digits are not ...
by cmjones01
Mon Jan 16, 2017 8:46 pm
Forum: hardware
Topic: A request for rare 32016 based hardware
Replies: 48
Views: 3205

Re: A request for rare 32016 based hardware

I've just run CLOCKSP on my 32016, under BAS32 rather than as an executable (doh!). The results are consistent and fairly underwhelming, apart from the trig functions. IMG_20170116_213957.jpg For those of you viewing in black and white, the results are: Real REPEAT loop 3.50MHz Integer REPEAT loop 3...
by cmjones01
Mon Jan 16, 2017 4:15 pm
Forum: hardware
Topic: A request for rare 32016 based hardware
Replies: 48
Views: 3205

Re: A request for rare 32016 based hardware

Ah, great. I'll have another go then! Thank you for the hints.

Chris
by cmjones01
Mon Jan 16, 2017 11:09 am
Forum: hardware
Topic: B+64k Special 12k?
Replies: 23
Views: 2915

Re: B+64k Special 12k?

Since I have a B+ in the office, I thought I'd try the code. It turns out that the screen inverts in both mode 1 and mode 129. I made a quick and dirty video here:

https://www.youtube.com/watch?v=5EASGCCPxVw

I hope that helps untangle the memory mapping puzzle!

Chris
by cmjones01
Sun Jan 15, 2017 8:27 pm
Forum: hardware
Topic: A request for rare 32016 based hardware
Replies: 48
Views: 3205

Re: A request for rare 32016 based hardware

I also dug around in the Panos help and found that there should be a 'date' command to set the date and time, but it doesn't appear to exist on any of the 6-disc Panos set that I've got...

Chris
by cmjones01
Sun Jan 15, 2017 8:26 pm
Forum: hardware
Topic: A request for rare 32016 based hardware
Replies: 48
Views: 3205

Re: A request for rare 32016 based hardware

OK, I found a floppy disc that wasn't worn out and transferred test-32016.dsd. Panos 1.4 boots fine, but when I try to run 'pi', I get 'Exception: Time not set'. This is on a standard BBC B. I haven't dug out my Master to see if its RTC would help. IMG_20170115_212442.jpg I tried running clocksp at ...
by cmjones01
Sun Jan 15, 2017 5:18 pm
Forum: hardware
Topic: A request for rare 32016 based hardware
Replies: 48
Views: 3205

Re: A request for rare 32016 based hardware

I've got UPURS running now so should be able to try out the Panos version properly. I would have done it last night but the floppy I was using for the transfer went bad (it was an old battered one I'd been using for testing and repairing all sorts of dubious floppy drives).
by cmjones01
Fri Jan 13, 2017 10:39 am
Forum: hardware
Topic: A request for rare 32016 based hardware
Replies: 48
Views: 3205

Re: A request for rare 32016 based hardware

Thanks for the info Chris. I note that the RAM chips are from mid-1985 and the CPUs are from early 1984: I'm tempted to conclude that Acorn bought a slew of CPU chips and subsequent sales of 32016 copros were not so great. It's also possible that NatSemi made a load of CPU chips in '84 and they wer...
by cmjones01
Fri Jan 13, 2017 10:17 am
Forum: hardware
Topic: A request for rare 32016 based hardware
Replies: 48
Views: 3205

Re: A request for rare 32016 based hardware

You're welcome. It's fun to be able to contribute to this league table of CPU performance. I'd heard that the 32016 had a reputation for being a bit rubbish performance-wise, and these results seem to reflect that. The co-pro does indeed have a 12MHz crystal and 150ns RAM, so will be running at 6MHz...
by cmjones01
Fri Jan 13, 2017 10:11 am
Forum: software: other
Topic: XFER problems when sending .SSD
Replies: 6
Views: 534

Re: XFER problems when sending .SSD

I think I'll give UPURS a try. I'm pretty sure I've got all the necessary bits lying around to make a cable.

Dave, thank you for the hints about ADT and TREECOPY, but in this case I'm trying to transfer a disc image from a PC to the Beeb, rather than between filing systems on the Beeb itself.

Chris
by cmjones01
Fri Jan 13, 2017 7:30 am
Forum: software: other
Topic: XFER problems when sending .SSD
Replies: 6
Views: 534

Re: XFER problems when sending .SSD

sweh wrote:Silly question... Is the disk formatted?
There's no such thing as a silly question...but yes! It is.

Chris
by cmjones01
Thu Jan 12, 2017 9:30 pm
Forum: hardware
Topic: A request for rare 32016 based hardware
Replies: 48
Views: 3205

Re: A request for rare 32016 based hardware

I've also transferred the pi-bbc-32016.asm file but have no way of assembling it under PanOS yet...

Chris