Standard practice to use r/w on dir pin ( microtan 65 buffer all i/o and r/w is used for dir on 74ls245 buffer)
r/w is use to drive dir on the 74ls245 on the microdisc circuit as well. so I do not know want you on about?
Also there is 4 i/o not buffered at all at the cumulus end 3v3 logic pulled to 5v rail via resistors, that is a no no (R1,R2,R4 and R5)
I would never do that, you would translate the logic with dual voltage buffers as done with the data bus.
You can get away with 5v logic out from oric to 3v3 logic into the cpld because cpld is 5v logic tolerant
But to have 3v3 logic o/p from the cpld to drive 5 v logic i/p on the oric bus end via a cable is asking for trouble ( yes I seen it done on eg: coco sd and others but the bus connection is very short.
If you think you just need to buffer the cumulus end go right ahead, will end up with the same problems as as before (if the cable is short you may be ok as Retromaster stated "works with short cable but not long cable"
I have hi-lighted what tests should be done to iron out the problems ( see previous posts)
Bad idea to tell customers that it works on my machine but it may or not work on yours as it is the case now
Sort out the buffer at cumulus end ie 3v3 logic to 5v logic then test with different length cables ( without buffer at oric end)
Then proceed to buffer the oric end then test with different length cables.
Do get me wrong I want this project to work.
My mods were based on present main board design not a new design you propose.
If you do use buffers on new layout you need to translate all 3v3 logic to 5v and 5v to 3v3 logic and remove R1,R2,R4 and R5.
The reason I choose one bi-directional buffer instead of a mix of bi-directional and single directional buffers for all i/o is it cuts the price down when you buy 100's and also cannot find dual voltage single directional buffers
The buffer I would use allows all logic combinations and bi-directional making it truly universal.
There may well be a problem with the map signal being generated from 02 signal and 32Mhz crystal oscillator (oversampling)
The Oric Atmos is very fussy with the timing and jitter on that signal.
If you are going to resign the project please let me know as there no point in me doing so ( I am considering it)
Also let people know that the project is going to be resigned and when likely production run would start.
At the moment I think people believe the design is current and does not change and when is production run who knows?