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Thread: Osi c4p

  1. #51
    Join Date
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    Hi Daver2, et al.

    Quote Originally Posted by daver2 View Post
    So POKE 56832,5 should be 64 column, no sound colour. Use that instead for the poke.
    Dave
    Sorry, my bad!

    Should be "5", not 4.

    Was testing something with the 32 column mode disabled.

    Cheers,
    Red

  2. #52
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    Hi Falter, et al.

    Quote Originally Posted by falter View Post
    According to my manual, POKE 56832,4 *should* be 32 character, sound off, color on, and that's what it seems to do, yes. Not sure what's up with Red's there.

    ..... I will do a quick test to see how many rows I'm getting.

    I just did a 'test' for the number of lines available - I hit Return 27 times before OK prompt disappeared up top. So I'm thinking something is still off with the vertical, maybe a bad counter still in there somewhere. I seem to recall powering up once and having zero until I swapped two of them around. Regrettably, I don't have any more 163s kicking around to swap in.
    My bad on the "4" value, sorry for the bum steer! Should indeed by "5". Took the screen shot when I was testing something with the 32 column mode disabled.

    28 rows sounds correct.
    Normally the monitor is hardcoded to 64 columns x 28 rows.

    You'll need to burn a new monitor ROM if you want the full 64x32 visible.

    Example from the CEGMON source code:

    START = 128 ; SET SCREEN OFFSET
    COLS = 64 ; SET COLUMNS TO DISPLAY
    ROWS = 28 ; SET ROWS TO DISPLAY

    SWIDTH = COLS-1
    TOP = SCREEN+START
    BASE = ROWS-1*WIDTH+TOP
    BOT = SIZE+1*1024+SCREEN


    I'm sure I have the memory locations to change somewhere amongst my docs here....

    ---

    BASIC knows nothing about the Colour RAM area, and makes no attempt to clear or otherwise initialise it.
    You'll have to do it yourself, like in my example.

    Cheers,
    Red

  3. #53
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    Hi Falter,

    Quote Originally Posted by falter View Post
    Hmm.. nope.. I get this:

    Attachment 58352

    I can see it drawing out all the characters when I run the program, although they disappear above the visible range of the screen. But as soon as I run the color invocation, it does as you see there.
    Looks like colour memory is being written to OK.

    First two lines on the pic you attached show the colour patterns looking the same as my example.

    Try:

    # init half the colour ram to regular patterns
    10 FOR T = 0 TO 255
    22 POKE 57344+T,T
    24 POKE 57600+T,T
    26 POKE 57856+T,T
    28 POKE 58112+T,T
    30 NEXT

    # character set to lines 5-8
    40 FOR T = 0 TO 255
    50 poke 53760+T,T
    60 NEXT

    # colour on, and keep running
    70 POKE 56832,5
    80 GOTO 80
    RUN

    Cheers,
    Red

  4. #54

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    Hi Red, another person from Sydney. 3 more posts, and you won't be moderated any more.

    I wonder if the c4p rom is the same as the other OSI roms... hmm

    Looks like this c4p is working, or just about.

  5. #55
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    Hi Robbbert,

    Quote Originally Posted by Robbbert View Post
    Hi Red, another person from Sydney. 3 more posts, and you won't be moderated any more.

    I wonder if the c4p rom is the same as the other OSI roms... hmm

    Looks like this c4p is working, or just about.
    Yep, we know each other already from the MSPP (amongst other places...)

    The pics that Falter has posted look like the machine is fitted with the "SYN600" roms, which contain code for *all* the OSI machines (IIRC).
    The jumpering on the board being used determines which code blocks are visible.

    I think the machine is working ok too. Colour ram appears to be OK.
    I have another post (waiting to be approved) which will test the colour ram

    Cheers,
    Red

  6. #56
    Join Date
    Jun 2012
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    UK - Worcester
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    >>> Sorry, my bad!

    No problems. It was just something I noticed in passing that didn’t line up with the documentation, so I thought I would mention it in passing.

    Worth knowing that the colour memory isn’t initialised. However, from my research, that would indicate the possibility that the B & W display will be a bit ‘random’ in that the least significant bit of the colour memory is used to invert the data bits from the video dot shift register via U2B...

    Nice to have you both in the thread! It is a bit of a pain being moderated, but it does keep the spam down big time. QDOS to the mods for this thankless task!

    Dave

  7. #57
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    I have checked the schematics again today and wish to correct my previous post...

    If the colour ‘bit’ is not enabled, then the latches on the output of the colour RAM will be permanently held in reset. This means that you can update the colour RAM whilst in B & W mode and it will have NO effect on the perceived screen image. It also means that my statement about the ‘invert bit’ having an effect whilst colour mode is disabled is FALSE.

    Dave

  8. #58
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    That's good to know about the number of rows, thanks Red. I was looking at my Challenger 2 last night and it seemed to be about the same number also.

    I followed the waveform patterns last night to check out the 123s, particularly the one that controls background color... but they seemed fine. I tried a swap anyway but it made no difference. Also swapped the 74L04 back in.. and interestingly the background, which had been more orange than before I swapped it, went back to being even more multi color.

    I don't know.. I wish I had a known good C4P to compare with.

    Am I wrong in thinking OSI gear in 79-80 was a bit dated design wise? I mean, my Atari 800 just seems ultra modern next to this thing, and the C4P and that came out around the same time. OSI rose that awful 48 long painfully grippy pin bus all the way to the end pretty much, meanwhile others were offering truly modern designs. It's not like they weren't charging a premium..

  9. #59
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    Probably the biggest difference is how much money the company had to spend on research and development. I suspect Atari had way more money to invest in (more) complex bespoke silicon than OSI did...

    Anyhow, back to your ‘problem’. I have pulled my old video books out of storage and given the relevant chapters a good read whilst watching a couple of episodes of NCIS on the TV.

    There is a ‘warning’ in the manual “U1B must be replaced by original type to obtain proper colour”. This IC (or more importantly its timing) is critical.

    After the horizontal synch. signal should come a colour burst. I think this is produced by the 74123 U4A. This colour burst is a few cycles of the frequency from CD0. This signal is the reference signal by which the colours are encoded, decoded and displayed. The 74L04 acts as a (very) crude delay line. The desired ‘colour’ is selected by choosing one of the eight phase delays fed into 74151 U1A (noting that D0 is wired to 0V meaning no chroma component - just the brightness or luma component = black or white).

    By filling 16 bytes of contiguous colour memory with the values from 0 through 15 (with a half white / half black character in the corresponding character memory) should permit us to work out what is going on.

    I will post a program in a few minutes...

    Dave

  10. #60
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    Try this...

    10 POKE 56832,5
    20 FOR I=0 TO 15
    30 POKE 53760+I,14
    40 POKE 57856+I,I
    50 NEXT I

    This should display 16 little houses at the beginning of the 8th line down, each in a different foreground/background colour combination. The colour order should be: yellow, inverse yellow, red, inverse red, ... following the colour numbers 0 through 15 in the manual.

    The manual I am referring to is http://www.osiweb.org/manuals/c4man.pdf. Page 28 describes the colour codes whilst page 110 identifies the little house symbol (code = 14 = $0E).

    Over to you. What do you get?

    Dave
    Last edited by daver2; December 31st, 2019 at 08:05 AM.

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