Search found 9 matches

by Danjovic
Wed Aug 07, 2019 12:28 am
Forum: Development
Topic: Jupiter ACE Kit /sorry half off-topic! :)/
Replies: 18
Views: 8819

Re: Jupiter ACE Kit /sorry half off-topic! :)/

You can add backporch capacity with some spare gates and have a video signal with correct output impedance and amblitude with mere 3 resistors (link1) (link2) ;)
Image
by Danjovic
Tue Jul 30, 2019 6:11 am
Forum: Hardware
Topic: Tape Loading
Replies: 4
Views: 836

Re: Tape Loading

1024MAK wrote:
Mon Jul 29, 2019 5:45 pm
Have you studied the ZX80 schematic?

Mark
Yes, I have studied the zx80 and some zx81 clones, and all of 'em use a capacitor in series thus forming a high pass filter but then again a low pass filter would make more sense.
by Danjovic
Mon Jul 29, 2019 4:13 pm
Forum: Hardware
Topic: Tape Loading
Replies: 4
Views: 836

Tape Loading

Hi folks. I am routing a custom version of ZX97 board and after reading some material about tape loading I got concerned about what should I use as a front end on the input buffer pin (ear). I haven't found answers on the plenty articles and posts I have researched, not even on the ROM lisiting avai...
by Danjovic
Tue Aug 21, 2018 3:46 am
Forum: Hardware
Topic: Improving Timex/Sinclair Tape Loading
Replies: 153
Views: 43205

Re: Improving Timex/Sinclair Tape Loading

Thanks people for sharing this amazing project. I have routed a couple of boards for this project, being one for use with a box by Hammond, reference 1455C801 and AAA cells but can also be used standalone as it has mounting holes. I have used stereo jacks for input/output as such parts are very easy...
by Danjovic
Sun May 24, 2015 1:11 am
Forum: Development
Topic: Kolour
Replies: 14
Views: 3071

Re: Kolour

If you use a 74LS688 or 74HCT688 MAGNITUDE/IDENTITY COMPARATOR you can test for /WR low, /MREQ low plus 7 address lines (say A9 to A15) all in one chip. Data sheet (PDF) here Mark Good point. I have some of these here, although they are a bit hard to find in local stores (at least harder than the '...
by Danjovic
Sat May 23, 2015 2:09 am
Forum: Development
Topic: Kolour
Replies: 14
Views: 3071

Re: Kolour

El voilà Danjovic, the full article! :-) It is in Portuguese, but it is not difficult to understand. To switch the display from normal to inverse, it is used POKE 65500. Greetings. Thanks! Portuguese is my mother language :). I am from Brasil! I think that the circuit can be enhanced by the use of ...
by Danjovic
Sat May 23, 2015 1:57 am
Forum: Development
Topic: Kolour
Replies: 14
Views: 3071

Re: Kolour

Be aware that the first five bytes of the rom are being written to by the floating point routines of the rom. Not only floating point, a simple PRINT command is enough to write to ROM at address 0. Uh oh, I didn't knew that. I am not so used in ZX81 architecture... Thanks for the advice! I'll try a...
by Danjovic
Fri May 22, 2015 3:53 am
Forum: Development
Topic: Kolour
Replies: 14
Views: 3071

Re: Kolour

Thanks! The main goal of the project is to allow to user to stick at the most pleasant color combination (fixed color configuration), but yes, I think is posible to perform the color selection by a poke, preferably by activating a latch using the ROM CS, thus allowing to type "POKE 0,nn" and change ...
by Danjovic
Sun May 17, 2015 11:30 pm
Forum: Development
Topic: Kolour
Replies: 14
Views: 3071

Kolour

For those who have a monitor that can cope with RGB video (Hsync @ 17.5Khz) like Samsung 510n. Here you are a circuit buit to allow to choose the foreground and background colors for ZX81 video using dip switches. Need separate positive sync, though. https://lh3.googleusercontent.com/-o-9vOSqGheA/VU...