16th Apr 2021, 12:06 pm | #1701 | |
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Re: Non-working Commodore PET 3016
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So although Aliexpress etc have MC3446D's quite cheap, they do show a picture of a Surface-Mount one - So not suitable. And these are TI's package details that are not in their datasheet, but found from: https://www.ti.com/packaging/docs/se...tipackages.tsp D (R-PDSO-G16) Plastic Small Outline Package: https://www.ti.com/lit/ml/mpds178g/mpds178g.pdf J (R-GDIP-T**) Ceramic Dual In-Line Package: https://www.ti.com/lit/ml/mgdi003/mgdi003.pdf N (R-PDIP-T**) Plastic Dual In-Line Package: https://www.ti.com/lit/ml/mpdi002c/mpdi002c.pdf So shows that MC3446N or MC3446J would also be OK for original MC3446P |
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16th Apr 2021, 12:19 pm | #1702 |
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Re: Non-working Commodore PET 3016
I agree that 'D' almost always means surface-mount, where 'N' almost always means DIP, although confusingly DIP ICs may not always end in 'N'.
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16th Apr 2021, 12:40 pm | #1703 |
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Re: Non-working Commodore PET 3016
I presume we are still agreed that MC3446AP is an acceptable substitute for MC3446N? Otherwise we may be causing Colin some anxiety here in our desire to be meticulous.
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16th Apr 2021, 2:53 pm | #1704 |
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Re: Non-working Commodore PET 3016
I think Colin can rest easy.
Alan |
21st Apr 2021, 2:10 pm | #1705 |
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Re: Non-working Commodore PET 3016
Just to let you all know I have the sockets and new MC3446AP ICs, the keyboard rubberised contact paste and a couple of port connectors for the user port (as I want to add a speaker).
I also have good weather for a change so I'm a bit busy being outside. I'll be back though soon with an update. Colin. |
21st Apr 2021, 11:47 pm | #1706 |
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Re: Non-working Commodore PET 3016
Acknowledged, Colin. As a regular visitor to Scotland, I know that a spell of good weather there is a gift never to be wasted.
I wonder if you went for a pair of the buffers, or three of a kind? |
22nd Apr 2021, 5:20 am | #1707 | ||||||
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Re: Non-working Commodore PET 3016
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And I discovered it did also check virtually-all the other lines on the port, including the four DAV, NFRD, NDAC and ATN ones that go through the 3rd (UA9) Buffer, and also EOI that has its own extra single output-buffer with direct unbuffered readback. So it's only SRQin that isn't tested - which goes straight to CB1 input on UC6(6520), that also does all of the IEEE Databits as well as some of the other IEEE handshaking lines (with UC5(6522) & UC7(6520) also being used for the remainder). After reading that User Port article, I had wondered how feasible it would be to fully-test from BASIC all of the lines using the 6520 / 6522's CA1/CA2/CB1 & CB2 - As you can only read the (interrupt etc.) flags set by these, and if the Kernal responds first then it can automatically clear them when it reads the registers. So it seems you can't use the UC5 6522's (User Port) CB2 as an input from BASIC, only as an output, as Port B's Control lines flags may get cleared automatically. And the older 6520's are actually a right pain to use (compared to more versatile 6522)., with only 2 register select lines - As there's a kind of register bank-switching bit in control registers and also some bits take on different functions depending on setting of Cx2 etc. So I had at first wondered how the single Poke & single Peek that SiriusHardware had listed would work if needing to keep switching the shared Data Direction / I/O Port register address function. But it's fortunate that Commodore decided to use separate Ports for Data input & output, so the data direction registers for these only had to be setup once in Kernal and you had permanent access to the Data Output & Data Input Port registers without having to keep toggling the register address function. So if the IEEE book's test program listing only reported Databits errors, then it seems the 3rd (UA9) buffer was still OK, and only UA7 & UA8 ones had failed. But it's not a bad idea to have a spare in case UA9 or one of the replaced Databits ones fails in future as these are getting more difficult to obtain at a sensible price. When the weather's not too good, then there's quite a few PET games to relive, as featured here: 20 Games That Defined the Commodore PET: https://www.youtube.com/watch?v=YKC8ARAWfhY Although about the only one I remember playing on one of my School's PET's during after school 'Computer Club' (I don't recall these computers being used for anything else at the time, until we a few years later there was a room of BBC ones) was this version of the Cosmic Guerilla arcade game: https://www.mobygames.com/game/pet/c...ak/screenshots Last edited by ortek_service; 22nd Apr 2021 at 5:46 am. |
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22nd Apr 2021, 5:58 am | #1708 |
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Re: Non-working Commodore PET 3016
I also found the Ruud's Commodore Site has a quite useful webpage about how the IEEE signals work: http://www.baltissen.org/newhtm/ieee.htm
And also some useful info on the 6520: http://www.baltissen.org/newhtm/6520.htm as even full Rockwell (compared to brief Commodore) datasheet on that isn't very clear on the exact operation (Although maybe the MC6821, which has been tested to work the same in these, has a better datasheet) |
22nd Apr 2021, 11:15 am | #1709 |
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Re: Non-working Commodore PET 3016
When I did some part-disassembly of the Kernel and EDIT PROMs I found the CPU jumped into a large subroutine in the EDIT PROM very soon after startup. One of the jobs that first subroutine does is to clear the screen RAM, and another is to set up the 6522 and 6520 ICs in a sane state so that by the time you get to a BASIC prompt those ICs have already been initialised.
I did notice the odd stray signal such as IFC, provided by UA10 pin 10, which has no inherent readback ability to allow it to be self-tested but it is essentially just a buffered reset signal out to the interface so that should not be too hard to check out. It will come to the point where the only way to be really sure that the IEEE 488 interface is OK is by trying to use it. That's not to say that we should not fix as many fixable / testable parts of it as we can, first. Last edited by SiriusHardware; 22nd Apr 2021 at 11:24 am. |
22nd Apr 2021, 1:31 pm | #1710 |
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Re: Non-working Commodore PET 3016
I got three - let's see how it goes with the first two.
I have a few spare chips which I will list soon that other people will be welcome to for their projects. Colin. |
22nd Apr 2021, 1:34 pm | #1711 | |
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Re: Non-working Commodore PET 3016
I had not twigged they were also known as HP-IB. That takes me back a long way - I used to do IT support for Colman's in Norwich a long time ago. They were a big HP shop with HP 3000s, HP 150 PCs, HP Vectra PCs and servers and all the Thinkjet, Scanjet and other peripherals that all used HP-IBs which were industrial strength and daisy-chainable.
That's when I came across vampire taps for thick ethernet too. Memories. Colin. Quote:
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22nd Apr 2021, 1:38 pm | #1712 | |
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Re: Non-working Commodore PET 3016
I remember Cosmic Jailbreak - thanks for the memory jog. I'll have to go through my tapes and see if I still have it.
A surprisingly high percentage of the games/applications on my 40+ year old tapes still load just fine. I was expecting many more problems with them than I have had. I guess I ought to somehow make a copy. Is the best way by using my tape recorder plugged into my PC using something like Audacity to create a copy? Colin. Quote:
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22nd Apr 2021, 1:55 pm | #1713 |
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Re: Non-working Commodore PET 3016
I'm not sure that a conventional tape player will 'play' a PET tape in the sense that you might expect because it isn't really Audio which is on the tape, but a linear series of positive and negative 'bar magnets' which the system lays down on the tape.
I wonder if it is possible to connect two datasettes back to back, data-out on the source connected to data-in on the destination? This is really outside of my experience though. |
22nd Apr 2021, 2:51 pm | #1714 | |
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Re: Non-working Commodore PET 3016
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I talked about this at an interview at the time, and the interviewer who was also the training officer said they had a spare official one in the cupboard, and gave it to me. So my home made interface didn't get any real use. Oh, and I got the job! |
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22nd Apr 2021, 3:04 pm | #1715 | |
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Re: Non-working Commodore PET 3016
I'll try the tape-to-computer thing and report back.
Colin. Quote:
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22nd Apr 2021, 3:24 pm | #1716 |
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Re: Non-working Commodore PET 3016
If you do, you need to use a line-in, not mic-in input on the PC and ideally a line-out rather than 'Ear' or 'Phone' output on the player.
I'm reasonably sure this won't work anyway, but I would be delighted to be wrong, and I don't think any harm can come from trying. |
22nd Apr 2021, 3:52 pm | #1717 |
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Re: Non-working Commodore PET 3016
I've seen programs that will "play" .TAP files from a computers sound card which can be recorded onto tapes and loaded into C64 machines. Since the tape circuit is identical for PET, VIC and C64 machines I think you can record the PET tapes into a computer and play them back. Its a common mod to the commodore tape drives to add a 3.5mm jack to allow audio to be injected into the tape heads to allow playback of TAP files from a phone or computer.
https://www.youtube.com/watch?v=DISA7FrPza4 |
22nd Apr 2021, 3:59 pm | #1718 |
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Re: Non-working Commodore PET 3016
Another way might be to use a Pi Pico (which has a very large onboard RAM) to read and store the digital data stream played in from a datasette and then send it back out, verbatim, to the same recorder in record mode. There would need to be a bit of level shifting between the datasette's 5V levels and the Pico's 3V levels.
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22nd Apr 2021, 5:00 pm | #1719 |
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Re: Non-working Commodore PET 3016
Many moons ago I successfully recorded C64 and VIC20 tapes using a twin deck audio cassette machine. Worth noting that the datasette doesn't attempt to record digital type signals because it can't. This topic was discussed recently and at some length in the other PET thread.
Alan |
22nd Apr 2021, 7:01 pm | #1720 |
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Re: Non-working Commodore PET 3016
Quick update - I have another datasette (white with a tape counter) which now works after a belt replacement. I have a third datasettes (normal black) which has had the belt replaced and functions electrically (ie it rewinds/ff), but it does not load known working programs.
None of the three datasettes get any power from the PET port 2 - where can I start checking for power please? Thanks. Colin. |