Makey@LOGICON.ARPA (Jeff Makey) (08/26/86)
Is there any way to get TTL video output from an 800XL without building
some sort of RF-to-TTL or composite-to-TTL converter?
:: Jeff Makey
Makey@LOGICON.ARPAjhs@mitre-bedford.ARPA (08/26/86)
It looks to me as though the voltage level and impedance out of the "composite luminance" port of the 800XL should be about right to drive a TTL logic input, for what that's worth. At most, this would require one "comparator" IC to make sure the levels are right. Luminance is on Pin 1 of the 800XL jack, which, however, may not be where you would think Pin 1 would be placed! I am not familiar with what TTL monitors look like, so I can't give you a definitive answer. If it just looks for a single binary TTL level input, the above comments are about all you need. If it is a mult-bit digital input then you will need some kind of A/D converter if you want gray levels. If you are just doing word processing or otherwise can afford just two levels (black and amber or whatever) then you could run the single bit from Pin 1, either through a comparator/level converter or not, and run it through an inverter so you can turn it into two patterns with high contrast between them like 01111111 and 10000000. I hope this is of some help. Good luck with the project. -John Sangster, jhs@mitre-bedford.arpa
tob@inuxm.UUCP (T Burger) (08/28/86)
> Is there any way to get TTL video output from an 800XL without building > some sort of RF-to-TTL or composite-to-TTL converter? If you mean RGB TTL the answer is; You have to build something. If you mean a TTL version of the luminance signal then it is available inside the 800XL. The GTIA chip (U17) has 4 bits of luma on pins 31 bit 0 22 bit 1 23 bit 2 24 bit 3 25 sync these are buffered by a 4050 (U20) 6 bit 0 12 bit 1 4 bit 2 2 bit 3 15 sync Hope this helps. Ted Burger