Search found 365 matches
- Sun May 13, 2018 12:13 am
- Forum: Hardware
- Topic: Gigatron - TTL microcomputer
- Replies: 4
- Views: 1115
Hi, anyone stumble across this already? A simple 8 bit micro, with an EPROM and SRAM chip as main memory, but using only TTL chips for the CPU. 8-) :ugeek: (74HCT actually, for those of you playing along at home ;) ). Homepage: https://gigatron.io/ Aussie electronics boffin Dave Jones just did a rev...
Hmm too hot to touch though? It seems to be giving out more then 5V closer to 7 Or measuring wrong - seen often when people (try to) check voltages. For 78xx regulators like the 7805 in the photo, seen from the front (printed) side, pins from left to right are input, GND, output. So you'd put your ...
Much preferable over a RAM pack: https://web.archive.org/web/20150905141235/http://bitcycle.org/retro/zx81/internal_RAM/ Cheap, fairly easy, no RAM pack wobble, edge connector remains free for other add-ons like sound card, flash card storage etc. The original 16K RAM packs were poorly designed & an...
- Wed Apr 11, 2018 11:05 am
- Forum: Hardware
- Topic: ZX81 I/O interface for your projects
- Replies: 27
- Views: 6076
74HC -> 74LS: no problem, unless you're driving many LS inputs at once. In that case check datasheets / calculate load currents etc. 74LS -> 74HC: often works fine. In general, just check properties of IC where a signal comes from (and check datasheet of the HC part where it goes to). Better: add a ...
- Sun Apr 01, 2018 1:15 am
- Forum: Hardware
- Topic: Tape read/write on expansion port?
- Replies: 24
- Views: 3003
You must remember for port $FE to work correctly you use open collector drivers only.. DO NOT DRIVE DATA LINES HIGH. So you see the ula can if it's wants drive a data line low , or an external device can drive it low. High is created by the pull-up when nothing drive it low. Commonly known as " wir...
- Thu Mar 29, 2018 2:51 am
- Forum: Sinclair Misc
- Topic: Why the difference in TV out port?
- Replies: 2
- Views: 1016
At least for the TS1000, RF (TV) output is on V HF channel 2 or 3. Versus U HF channel 36 on a regular (UK) ZX81. Also note the channel select switch on the bottom, which is not present on a UK ZX81. And the somewhat-conductive silvery paint + metal strip inside the case on US models (for EMI shield...
- Fri Mar 16, 2018 1:42 am
- Forum: GAMES
- Topic: Copyrights for New Generation Software games (e.g. 3D Monster Maze)
- Replies: 5
- Views: 1254
This might be the worst advice ever, but: you could always just publish it and see what happens. Second that. If "just remove offending title if a copyright claim is received" works for you, then why not just go ahead. Ah yes, the -mostly theoretical- risk of legal problems / monetary damages etc. ...
- Wed Mar 14, 2018 2:14 am
- Forum: Development
- Topic: do we still use UHF modulators ?
- Replies: 17
- Views: 2023
Looks like close to standard composite voltage levels the modulator wants, apart from a DC bias (say, series capacitor or so?). Sadly there's no info on typical input impedance for that modulator. :?: it does mean that broken zeddies which are not comp modded won’t be fixable with this ULA (..) Quit...
@McKlaud and Andy: NICE!!! :) Especially Andy's 45-degree placement of the CPLD is likely how I'd have done it myself. The power consumption is roughly 250mA, but I have also got a 16KB SRAM chip on this board. I think I could go even lower if the 7805 were replaced with any decent DC-DC converter. ...