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  • daver2's Avatar
    Yesterday, 11:12 AM
    It didn’t sound like that when I played it on the recorder... Perhaps a bit more work required on the audio front! Good quality video though. ...
    29 replies | 1348 view(s)
  • daver2's Avatar
    Yesterday, 12:00 AM
    daver2 replied to a thread No serial output on PDP-11 in DEC
    So, something is running on the bus that the SIO is connected to... Have you got the means to check if pins 35 and 36 go LOW simultaneously (e.g....
    23 replies | 449 view(s)
  • daver2's Avatar
    January 18th, 2020, 01:25 PM
    daver2 replied to a thread No serial output on PDP-11 in DEC
    You can also look for activity on the following pins: 35 = /CE (must be low to select the SIO). 36 = /IORQ (must be low to select the SIO). 32 =...
    23 replies | 449 view(s)
  • daver2's Avatar
    January 18th, 2020, 12:51 PM
    daver2 replied to a thread No serial output on PDP-11 in DEC
    See my previous post #2 regarding CTS and the transmit and receive clocks. Dave
    23 replies | 449 view(s)
  • daver2's Avatar
    January 18th, 2020, 11:47 AM
    daver2 replied to a thread No serial output on PDP-11 in DEC
    Always worth a shot! Unfortunately, I think you are just going to have to do some 'computer archeology' and try and track down someone who knows...
    23 replies | 449 view(s)
  • daver2's Avatar
    January 18th, 2020, 11:20 AM
    daver2 replied to a thread No serial output on PDP-11 in DEC
    Thanks, I am starting to remember this now... The chips on those boards look like this is a heavily bespoke system (i.e. it is not a general...
    23 replies | 449 view(s)
  • daver2's Avatar
    January 18th, 2020, 09:27 AM
    daver2 replied to a thread No serial output on PDP-11 in DEC
    What on earth have you got there? The TMS9937 is a single chip video controller! I also see you have two (2) Z80 SIO chips - so what makes you...
    23 replies | 449 view(s)
  • daver2's Avatar
    January 17th, 2020, 01:29 AM
    daver2 replied to a thread No serial output on PDP-11 in DEC
    What about Clear to Send? Are you looping back Request To Send to Clear To Send? PDP-11 stuff generally doesn't use these lines - but this uses a...
    23 replies | 449 view(s)
  • daver2's Avatar
    January 15th, 2020, 03:00 PM
    daver2 replied to a thread Osi c4p in Other
    The best way is to learn to clear the screen (video and colour memory) and setup colour mode. Write your own subroutine and call that at the start of...
    103 replies | 2430 view(s)
  • daver2's Avatar
    January 15th, 2020, 01:00 AM
    daver2 replied to a thread SoC MK14 in Other
    What, A NASCOM 1 and now an MK14 :-)! Your British computer collection is expanding... >>> Yes I've heard some uncomplimentary things about the...
    9 replies | 211 view(s)
  • daver2's Avatar
    January 14th, 2020, 03:16 AM
    daver2 replied to a thread Osi c4p in Other
    >>> This is all making sense except for the angles thing Nope, nothing to do with the CRT at all... It is just a different way of describing...
    103 replies | 2430 view(s)
  • daver2's Avatar
    January 13th, 2020, 01:26 PM
    daver2 replied to a thread Osi c4p in Other
    It's more likely that there are so many manual adjustment potentiometers that getting it adjusted correctly is a nightmare :-)! You have digital...
    103 replies | 2430 view(s)
  • daver2's Avatar
    January 13th, 2020, 01:02 PM
    daver2 replied to a thread Osi c4p in Other
    Just had another thought whilst looking at the schematics and Terry's website. There are various components that should be removed if the OSI is...
    103 replies | 2430 view(s)
  • daver2's Avatar
    January 13th, 2020, 12:49 PM
    daver2 replied to a thread Osi c4p in Other
    You can have a colour on black or black on a colour. That's it... You can't have two colours in a particular character position. The pixels are...
    103 replies | 2430 view(s)
  • daver2's Avatar
    January 12th, 2020, 11:44 AM
    daver2 replied to a thread Osi c4p in Other
    >>> Hope your business trip was more exciting than my non-business trip here. The beatings will continue... I have just edited my post to...
    103 replies | 2430 view(s)
  • daver2's Avatar
    January 12th, 2020, 10:48 AM
    daver2 replied to a thread Osi c4p in Other
    Ready for the next instalment? Look at the schematic on page 6 of 8 of http://www.osiweb.org/manuals/OSI-540B.pdf. With the colour disabled...
    103 replies | 2430 view(s)
  • daver2's Avatar
    January 12th, 2020, 05:39 AM
    daver2 replied to a thread Osi c4p in Other
    Welcome back... Just got back from my business trip late on Friday - so still recovering... Also, just got back from Church and about to have...
    103 replies | 2430 view(s)
  • daver2's Avatar
    January 5th, 2020, 12:49 PM
    The version of BASIC in the ROMs is associated with the part numbers of the individual ROMS. If you look here...
    275 replies | 7778 view(s)
  • daver2's Avatar
    January 5th, 2020, 07:42 AM
    Bad page 0 or 1 RAM means that the ROMs will never work at all... You should get the hardware initialised and the screen cleared, but after the...
    275 replies | 7778 view(s)
  • daver2's Avatar
    January 5th, 2020, 06:36 AM
    Do you get the 'P' with or without the NOP generator fitted? Presumably without... With the NOP generator fitted you should just get random...
    275 replies | 7778 view(s)
  • daver2's Avatar
    January 5th, 2020, 06:13 AM
    Every day another step forwards! One of the bits of the PIA is sensed at start-up and (if active) the machine code monitor is entered. Now you...
    275 replies | 7778 view(s)
  • daver2's Avatar
    January 5th, 2020, 03:54 AM
    daver2 replied to a thread Osi c4p in Other
    >>> And I am curious what you're up to with the PDP code! I have designed a PCB for a TTL implementation of a PDP-8 (if you have been following...
    103 replies | 2430 view(s)
  • daver2's Avatar
    January 4th, 2020, 02:58 PM
    I think we did - that's where we saw that funny voltage level in the first place. EDIT: Yes, back in post #212... With my comments regarding a...
    275 replies | 7778 view(s)
  • daver2's Avatar
    January 4th, 2020, 02:28 PM
    daver2 replied to a thread Osi c4p in Other
    Just being lazy and posting the links I need for my subsequent posts... http://www.osiweb.org/manuals/c4man.pdf ...
    103 replies | 2430 view(s)
  • daver2's Avatar
    January 4th, 2020, 02:27 PM
    And also check the data bus lines for any signs of 'funny values' (like 1.6 Volt levels) as this would indicate problems on the data bus still -...
    275 replies | 7778 view(s)
  • daver2's Avatar
    January 4th, 2020, 11:39 AM
    daver2 replied to a thread Osi c4p in Other
    The next thing is a simple BASIC program to display a screen full of a specified character in a specified colour - and to sit there for ever and a...
    103 replies | 2430 view(s)
  • daver2's Avatar
    January 4th, 2020, 10:03 AM
    daver2 replied to a thread Osi c4p in Other
    No problem. We are going to have to teach you a bit more about schematics. A New year resolution I think :-)! Here is the first instalment. I am...
    103 replies | 2430 view(s)
  • daver2's Avatar
    January 4th, 2020, 08:16 AM
    Yep. Plus check for the video synch/blanking signal that feeds the peripheral chip that provides the interrupt. Dave
    275 replies | 7778 view(s)
  • daver2's Avatar
    January 4th, 2020, 03:00 AM
    This was my concern - in that there is something fundamentally wrong with the PET somewhere which is preventing the I/O sub-system from working...
    275 replies | 7778 view(s)
  • daver2's Avatar
    January 4th, 2020, 12:44 AM
    daver2 replied to a thread Osi c4p in Other
    I have finally worked out how this horrid circuit works. I will need access to my machine with a ‘real’ keyboard for the long post required - so it...
    103 replies | 2430 view(s)
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