The comments in the source are merely documenting as I figure out how the hardware works. The only question I have about the software is that now it is using a 6545 rather than a 6845, is there a speed/code size advantage by using row/column addressing rather than straight binary? Considering the board has no graphics capability and plenty of video RAM, it may speed things up even more. Just a thought.
Regards
David
On 28/09/12 09:19, Douglas Goodall
wrote:
David,
The VDU code you are working with was actually based on code that I wrote whileat DRI for the Olympia "PEOPLE" machine, which was a non-PC compatible builtby the Olympia typewriter company in Wilhelmshaven (not sure of the spelling) inGermany. The XIOS was implemented to support both VT52 codes for wordstar andalso a private set of escape sequences that were Olympia specific. Also supportedwere a set of escape sequences that allowed the programming of soft function keys.There was also a separate program called "function.a86" that had a gui and used thespecial escapes to alter the function table in memory. Being a European company,the 6845 initialization bytes were appropriate for the Olympia supplied monitor andother from the region.
If you have a question about the code, let me know.
Douglas
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On Sep 27, 2012, at 3:02 PM, vk5dg <vk...@internode.on.net> wrote:
Hello Oscar,
I've recently got my VDU card running and have been adding comments to the source code as I discover new things about it. I can tell you that the firmware is set up for a PAL monitor - it works at 312 lines non-interlaced at 50 fields per second. Also the jumpers for the character clock must be set as K1 2-3 (pin 3 of the 74669 HI) and K2 1-2 (pin 4 of 74669 LO). This gives an output of 2 MHz for the CLK signal (pin 21 of the 6545-1). I'm using a 30 year old green screen monitor on my board and after some adjustment of the picture controls it has given a stable picture.
Hope this helps for a start.
Regards
David
On Thursday, 27 September 2012 18:28:41 UTC+9:30, oscarv wrote:Hi all,
I recently completed a whole set of N8VEM boards (VDU, Zilog Peripherals, Disk IO and the 6809 board) to expand my N8VEM.
I have one question on the VDU... this is quite an old board by now so I wonder if anyone still has answers!
The board works well with RomWBW 2.1 but the top line of the screen is always garbled. See the picture: the top line should just show 'dir'. Also, there is faint but unusual 'ghosting' below the 25th line (second picture).
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I've read in the old postings that the 6545 CRT chip sometimes needs tweaking of screen parameters, but I doubt that is the problem here - I get the exact same picture on two monitors. Both are PAL monitors but both are supposed to be able to deal with NTSC (I don't think that is where I should look for a solution). One monitor actually developed a scary crackling noise after 10 minutes - but that may be unrelated, as it hasn't been used for more than an hour in this century.I'm not sure where to start my bug hunt - any suggestions are very welcome!
Regards,
Oscar.
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