Changes
:Yes, fragments of it do have some purpose. It's just terribly overcomplicated. You've seen the original Schneider solution (the other schematic on the same page), don't you? They used only 2 chips, not 5 chips for port decoding. --[[User:Nocash|Nocash]] 19:59, 10 May 2010 (UTC)
Ah, ok, now I understand why you think it's nonsense... But you're missing some background information about the schematic. The original circuit was a modular design, with one address decoder that was used on several projects and all projects were compatible with each other and could be expanded much further. As far as I can remember, there was a 24bit I/O Port, 8bit Printer Port and even an EPROM burner, which all used the same decoder and all of them could even be built in parallel together on one board, so the decoder has a lot of potential, that's not being utilised on this particular project. The other 4 outputs on the 74LS138 were used for the other expansions, but obviously they are overkill if all you wanted was the RS232 Port. Does it make more sense now?
Bryce.
