On 21/12/2016 03:23, "allison" <ajp...@verizon.net> wrote: >> If one of the other outputs is driving a CMOS device the output may >> not go high enough to satisfy it, however I would expect the reset >> input on the 8085A to be TTL compatible. > The 8085 reset input is not TTL, its schmidt trigger, and the level is > at the upper level for TTL. > If you use a 1K pullup then TTL, or open collector parts can be used as > well as CMOS.
That explains the pullups I've seen on other 8085 devices I've found in boxes recently like the Open University HEKTOR 8085 trainer. > The 8085 was designed to have simple reset for cost sensitive aps where > the circuit was usually > 22K pullup and 1uf to ground. > > If you using anything a 74HCxx would easily satisfy the drive and loading. I think I've got a couple of 74HC08s that would do nicely, cheers! -- Adrian/Witchy Binary Dinosaurs creator/curator Www.binarydinosaurs.co.uk - the UK's biggest private home computer collection?