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  • daver2's Avatar
    Yesterday, 10:34 PM
    daver2 replied to a thread Mark-8 Clone Project Begins in Other
    Nice look! Dave
    74 replies | 6929 view(s)
  • daver2's Avatar
    September 17th, 2018, 11:15 AM
    More PETs... The more the merrier... Welcome to VCFED. Dave
    223 replies | 9046 view(s)
  • daver2's Avatar
    September 15th, 2018, 11:51 AM
    If you have a 'kettle' lead on your PET - it probably contains an RFI filter - and this is possibly the culprit. Dave
    11 replies | 211 view(s)
  • daver2's Avatar
    September 15th, 2018, 09:19 AM
    daver2 replied to a thread Bigboard II in Other
    The cable you identified is/was designed for an IBM PC parallel (Centronics) port. I don't think there was a specific cable. I think what you will...
    16 replies | 407 view(s)
  • daver2's Avatar
    September 15th, 2018, 08:08 AM
    daver2 replied to a thread Bigboard II in Other
    Falter, Note that what you have referenced on ebay is a 26 way IDC to 25 way D adaptor. 25 pins of the IDC connector will be wired to the 25 ways...
    16 replies | 407 view(s)
  • nockieboy's Avatar
    September 14th, 2018, 02:28 PM
    Thanks Dwight - was just interested to know how it would work. I don't have a DMA in my system - was planning on putting one in, but they're not...
    25 replies | 388 view(s)
  • nockieboy's Avatar
    September 14th, 2018, 01:43 PM
    Well, my system is running quite happily at 4 MHz with a 125 kbaud terminal via interrupts? The ISR is pretty tight, so maybe that helps. I'm...
    25 replies | 388 view(s)
  • daver2's Avatar
    September 14th, 2018, 10:12 AM
    Yes, the first test (before anything else) is to disconnect both the monitor and the PET main board from the power supply itself (just leaving the...
    11 replies | 211 view(s)
  • daver2's Avatar
    September 10th, 2018, 11:11 AM
    daver2 replied to a thread Tektronix 4052 emulator. in Other
    It is still not working - but it is not working for potentially the right reason now - if that makes sense?! I think I now need to 'fix' the...
    34 replies | 692 view(s)
  • daver2's Avatar
    September 10th, 2018, 11:01 AM
    daver2 replied to a thread Sketchy auction in Rants
    If I am interested in an item - I put my maximum bid on it and that is that. No messing about. If some other people want to play games with bids -...
    6 replies | 188 view(s)
  • daver2's Avatar
    September 10th, 2018, 10:27 AM
    If you can dig that up I would make an Altair clone just to demo it! Dave
    6 replies | 187 view(s)
  • daver2's Avatar
    September 10th, 2018, 09:33 AM
    daver2 replied to a thread Tektronix 4052 emulator. in Other
    Downloading now Al... dave_m: the two devices used in the pipeline are 273 and 374 - both of these are low->high latch. Dave
    34 replies | 692 view(s)
  • daver2's Avatar
    September 10th, 2018, 04:31 AM
    daver2 replied to a thread Tektronix 4052 emulator. in Other
    Yep, you're right! a 373 is the transparent version and the 374 is the high-going edge triggered version. I think the problem was it was late at...
    34 replies | 692 view(s)
  • daver2's Avatar
    September 9th, 2018, 10:33 AM
    daver2 replied to a thread Tektronix 4052 emulator. in Other
    Still not working - but I have just had a thought (something along the lines of a pipeline issue). What if the flag register changed on every rising...
    34 replies | 692 view(s)
  • daver2's Avatar
    September 9th, 2018, 08:59 AM
    daver2 replied to a thread Bigboard II in Other
    I don't think (from what I've read) you will get a prompt until the monitor sees a <CR> from the parallel keyboard or one of the serial ports. ...
    16 replies | 407 view(s)
  • daver2's Avatar
    September 9th, 2018, 08:24 AM
    daver2 replied to a thread Tektronix 4052 emulator. in Other
    It's a '374 according to the schematic. Latch / flip-flop - the TI data sheet appears to use them interchangeably. The key thing is that the...
    34 replies | 692 view(s)
  • daver2's Avatar
    September 9th, 2018, 07:34 AM
    daver2 replied to a thread Tektronix 4052 emulator. in Other
    Many thanks Monty for the help you have given. So, not done a full check of the microcode ROMs - but a very 'quick and dirty' sample check of...
    34 replies | 692 view(s)
  • daver2's Avatar
    September 9th, 2018, 04:37 AM
    daver2 replied to a thread Tektronix 4052 emulator. in Other
    Thanks Monty - you are a star! I have downloaded your files and will have a look through them shortly - although I see the addresses are doing...
    34 replies | 692 view(s)
  • daver2's Avatar
    September 8th, 2018, 11:23 AM
    daver2 replied to a thread Tektronix 4052 emulator. in Other
    We only really need one (good) set of traces and, even then, we don't actually need the traces themselves. The URAx bits form an address (lets say a...
    34 replies | 692 view(s)
  • nockieboy's Avatar
    September 8th, 2018, 10:39 AM
    :thumbsup: Thanks guys. :)
    25 replies | 388 view(s)
  • daver2's Avatar
    September 8th, 2018, 02:44 AM
    daver2 replied to a thread Bigboard II in Other
    You should just need +5V for the logic and +/-12V for the RS232 buffers. The unit contains an EPROM programmer. The programming voltage is...
    16 replies | 407 view(s)
  • daver2's Avatar
    September 7th, 2018, 11:14 PM
    daver2 replied to a thread Bigboard II in Other
    I saw a couple of these on e-bay, but decided not to go for them in the end. I did lookup the schematics though, so give me a short while to do a...
    16 replies | 407 view(s)
  • nockieboy's Avatar
    September 7th, 2018, 02:05 PM
    Interesting idea to go direct to the BIOS - might give that some consideration and bypass the BDOS completely, as I'm receiving anything from 128...
    25 replies | 388 view(s)
  • daver2's Avatar
    September 7th, 2018, 01:43 PM
    daver2 replied to a thread Tektronix 4052 emulator. in Other
    So, I have been looking a bit further at the microcode and found a few anomalies. The microcode instruction at address 0x03A ends up jumping to...
    34 replies | 692 view(s)
  • daver2's Avatar
    September 7th, 2018, 09:32 AM
    Yeah, Hi guys. Read what it says, not what you think it says... Been there, done that, got the tee shirt :-)! Dave
    25 replies | 388 view(s)
  • nockieboy's Avatar
    September 7th, 2018, 05:46 AM
    Hi durgadas! Yes, that was the problem - I wasn't testing A. I'd misread the information on the BDOS function - it said it returns zero if no...
    25 replies | 388 view(s)
  • nockieboy's Avatar
    September 7th, 2018, 02:58 AM
    Hi everyone, As the title suggests, I'm trying to receive a lot of pasted code into a terminal running CP/M 2.2 and would like to receive the data...
    25 replies | 388 view(s)
  • daver2's Avatar
    September 7th, 2018, 12:30 AM
    daver2 replied to a thread Tektronix 4052 emulator. in Other
    Yes, URA0 through URA9. I don't think URA10 is used (it was reserved for larger microcode ROMs as a later enhancement). If J207 3-4 is made then...
    34 replies | 692 view(s)
  • daver2's Avatar
    September 6th, 2018, 01:49 PM
    daver2 replied to a thread Tektronix 4052 emulator. in Other
    Everything I have looked at tonight in the emulator looks good. Still doesn't work yet though... I still can't see how it can work if it is...
    34 replies | 692 view(s)
  • daver2's Avatar
    September 6th, 2018, 12:45 PM
    Many years ago I came across IC sockets that had been 'life expired' in the factory by firmware changes before releasing the items to us. We had some...
    24 replies | 607 view(s)
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About daver2

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About daver2
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UK - Worcester
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SW/HW design engineer

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