[Timbucus]

A new 8154 restores the old functionality - looks like I have damaged the tri-state mode of the output pins on my other 8154... Also I have removed the CAP on A11 and I still do not have any problems with the corrupt CHARSET except when the extra memory module is plugged in obviously which lead me onto...

I did this as I could not get the falling man demo to run for some reason the Graphics/Text output line PA6 on the 8154 would always go low just after uploading and the code running - you can see it is still OK as he screen looks like the Matrix with blocks of characters falling - the same code on the new 8154 works OK. So I assume the old 8154 was allowing itself to become selected (something to do with the A11 or A8 used as CS lines maybe?) and data was being written to 0820 or 0806 to affect the state of the PA lines / bit PA6.

A11 now looks a lot better - even when I plug in my memory module - those who read the memory thread will remember that I did not have an 74HC02 or 74LS02 so I used a 7402 - well with that swapped for a 74LS02 A11 seems much healthier - if you look at the MK14 circuit it is driving a lot of chips so I suspect the TTL load was just too much for the SC/MP - this may also account for the 8154 issue...

Edit: The corrupt character on Charset even with the memory module is gone so that can be attributed to the weakened A11 which the Cap was probably not enough to overcome under the extra load.