Thread: Ortonview PCB
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Old 28th Jun 2021, 12:57 pm   #2
SiriusHardware
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Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,482
Default Re: Ortonview PCB

Just had a quick look, in the short term it is also going to need pads for 4 x SM or through hole (or both) small value capacitors from A8-A11 to 0V as they are they are the essential 'dirty fix' to solve the problem where the system kept writing to address 'n' in one or more pages.

More ideally, add 2 x 74LS365 (6 x bidirectional buffers) in the VDU address bus (same as per the original VDU) so that the VDU address lines are cleanly disconnected from the MK14 address bus when the VDU is not trying to access it. You will remember that on Ortonview, the address line outputs from the VDU are just put into input mode but that does not properly disconnect them from the MK14 address bus and causes some loading on A8-A11.

It would obviously be much more of a chore to wire these buffers up on a veroboard build but if there is to be a PCB, then the two extra sockets and ICs would add no more than five extra minutes on the build. I would say this would be more directly necessary than a noise / random generator although I do like that idea.

Needless to say, you can count me in for one of these if they ever get to the point of being made. If you get to that point let us know how much you are going to want for them and - sorry to have to say this, but I suggest you don't put the design files in the public domain.
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