Rob,

I try not to use the 7404 circuit, I had a bad experience with Micromint 8052 boards. They had a board that connected to the processor board that had a UART and a 8255 on board the UART was run via a crystal using the 7404 circuit. We were using these boards in a product and at some point in time Micromint changed the 74LS04 to 74HCT04 and now the board would not communicate at 9600 baud, but was ok at 2400 baud. I traced the problem down to the 74HCT04, replaced the 74HCT04 with a 74LS04 and now the board would communicate at 9600 baud. I had a heck of a time convinicing Micromint that they had a problem. We finally had to replace the 74HCT04 chip ourselves.

Jacob