Scorpio News |
May 1989 – Volume 3. Final Issue. |
Page 31 of 43 |
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AVC and EPROM card should now co-exist peacefully.
Please note, I never bend IC pins or solder to them, it’s just that it’s easier to describe things that way. I use an intermediate DIL socket and bend/solder the pins on that.
When I first tried out my AVC, all I could get on the display was a green screen of less than full height. I had chosen to ignore the advice in the manual where you are told to connect the N2 video into the AVC as I wanted to use a twin screen set up.
After much probing, I discovered that TP 6 (EXT VIDEO) was floating at about 1.6 volts plus, so I tried grounding it and bingo! everything burst into life! The ground pin is not marked as such, but you’ll find it immediately to the left of TP’s 8, 7 & 5 (/SYNC OUT, EXT /SYNC & EXT SYNC).
Doctor Dark had a similar problem with his PLUTO . I checked the wiring between my AVC and my Microvitec Cub 653 after reading his comments, but could find no errors. Which of us is right? Are we both right?
I’ve had a good hard look at my Nas FDC and at its circuit diagram. I think that the designer of the card always intended it to be able to handle an 8″ drive (as drive D) under software control via a spare latched port bit.
There are several strategically placed, innocent looking plated through holes in all the places where one might wish to tap into various tracks when modifying the card for an 8″ drive. The holes are big enough to take small test pins and most seem to serve no other purpose. Has anyone done the mods? If so I would like to know how. I can be contacted on ____ ______ between 8.00 p.m. and 10.45 p.m. most evenings.
Lucas CP/M does NOT require the AVC. It works perfectly well via the N2’s 48 x 16 display. It has screen editing (of the “unfixed” variety) and there’s a feature which enables you to send control codes to the printer directly from the keyboard. Also supplied are two Resident System Utilities: AVCTXT and AVCTXTS. The first is required when using graphics and it occupies 4.5K of RAM. AVCTXTS is a “switched” version which handles text only. The main feature of AVCTXTS is that its main and alternate set of characters are stored not in EPROM (as mooted by David Parkinson in a previous issue) but in the video margins (up to 4K per colour is available). Consequently it only occupies 2K of RAM. You need the AVC to use the RSU’s.
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