Sinclair ZX80 / ZX81 / Z88 Forums

Andy Rea wrote:i think it would be prudent to use an FPGA, or maybe a microcontroller ( avr , pic, propeller, ect ) with much faster clock rates that shod allow one to create any arbitrary waveform with the appropriate bitstream to create a teletext page.

I'm sure at least one (maybe more) micro-controller projects already exist. Sorry, I don't have a link.

Mark

dr beep wrote:How often could you 'refresh' the content of the page.

If frequently you can indeed use the settings of teletext as a screen and resolution.

This is not easy reading for me, but seems like a whole tele text screen can be fitted per frame.

mrtinb wrote:

dr beep wrote:How often could you 'refresh' the content of the page.

If frequently you can indeed use the settings of teletext as a screen and resolution.

This is not easy reading for me, but seems like a whole tele text screen can be fitted per frame.

Exactly, thus all kind of gameplay is possible.

dr beep wrote:How often could you 'refresh' the content of the page.

If frequently you can indeed use the settings of teletext as a screen and resolution.

(when it works the emulators must get add a TELETEXT screen)

As far as I know one page is transferred per frame in the top margin lines.
So about 50 pages per second, the TVs do it in a round robin manner but you could also decide to update only one single page (100 for example) or (as many stations do) update 100 every one or two seconds to get a faster picture while transferring the rest in other frames. I am a big fan of teletext and very important is to have a TV which can store 1000 pages or so. I hate waiting for a page to be transferred in memory page by page. This can take up to 10 seconds when changing pages without sufficient teletext memory.

This thread is about teletext (in TV) not Telex (!) or teletypewriter.

https://en.wikipedia.org/wiki/Teletext# ... xt_100.png

See also https://en.wikipedia.org/wiki/Ceefax and http://teletext.mb21.co.uk/

Mark

I thought that maybe the Max Demo was the solution, as it had greater resolution (320x240). But it seems Teletext needs a resolution of 360 pixels.

http://www.bighole.nl/pub/mirror/homepage.ntlworld.com/kryten_droid/teletext/spec/teletext_spec_1974.htm wrote:1.2 Data Line Structure

Each Data-Line comprises 360 bits which may be considered as 45 eight-bit bytes.