Hi,
I've built the 555 based circuit By Ziggurat http://zx.zigg.net/misc-projects/
I plan to use it on a ZX80 but meanwhile tested it with my CZ1000.. with a Ferranti 2C210E ULA which grates an appropriate back porch.
What I've noticed is a really crisp, steady and noiseless K cursor but with a black left border.. is this because the preexisting backporch added to the new one or did I messed up something?
Back Porch circuit and a back porch generating ULA
Back Porch circuit and a back porch generating ULA
Ernesto
ZX80 USA, ZX81UK, ZX Spectrum, ZX Spectrum+, ZX Spectrum 128+ UK, ZX Spectrum +2/A, Sinclair QL, CZ1000, CZ1500, CZ2000, CZ1000Plus, CZ1500Plus, CZ Spectrum, CZ Spectrum Plus, TK83, TK85, TK90X, TK95. TS2068. And more to come
ZX80 USA, ZX81UK, ZX Spectrum, ZX Spectrum+, ZX Spectrum 128+ UK, ZX Spectrum +2/A, Sinclair QL, CZ1000, CZ1500, CZ2000, CZ1000Plus, CZ1500Plus, CZ Spectrum, CZ Spectrum Plus, TK83, TK85, TK90X, TK95. TS2068. And more to come
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Re: Back Porch circuit and a back porch generating ULA
A longer black porch will eat into the left hand side border...
Mark
Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
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Looking forward to summer later in the year.
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
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- Joined: Thu Apr 23, 2020 6:02 am
Re: Back Porch circuit and a back porch generating ULA
You should be able to reduce the duration of the back porch by changing the RC values on the 555. Of course, then it may not work so well on the older ULA. Maybe a way to switch in different R values?
John