Erik,

There's an old military saying that, "Where you sit determines what you see."

Convenience determines cost, from where I sit, and I don't sit on an ivory tower where cost means nothing, but, since many of my applications have a maximum volume of 2 pieces, the man-hours involved in generating them are critical. If it's possible to use something that already exists, that saves on manpower. Also, the production cycle sometimes has to be very short, as short as two or three days from contract to delivery, in some cases, and quite often under a week.

Respinning PCB's, for example, involves risk. If I have boards made here in the U.S. I'm fortunate to have a 1% yield by the time they're assembled. That means that a board with $100 in total cost will cost as much as $10K just because of the low-quality manufacturing and assembly available here. Sadly, we don't take folks who show up intoxicated out back of the plant and shoot them in order to recover their salvagable organs for resale. The result is that we have to wait for a car crash if we need a liver transplant, while, in some parts of the world, they schedule them 4-5 days in advance.

I'm not high-volume enough, generally speaking, to justify having the boards made in China, where I'm almost certain to have a 100% yield. Unfortunately, if I have 'em made there, or in Korea, or in Taiwan, I'll have a competitor within a couple of weeks, who doesn't have the NRE to recover, if the volume is large enough to have 'em made there. Delivery from eastern Europe is too slow.

you say,
...It is NOT used bercause it is "sacred", it is used because it can generate 9600 - up which 12 can not. Today 22.1184 is gradually becoming the usual YES, "the usual" NOT "the sacred"...

but it's been shown in a couple of posts, perhaps even in this thread, that 12 can get within less than a percent of the required rate, and, of course, 12.288 MHz can hit it with 0% error.

you go on with,
"most of us do not live in an ivor tower where the cost of an external UART does not matter."

which I submit is pretty cheap when you're only building a couple.

and you say,
"where is the gain???????????? you get the same number of interrupts, you have to do the same processing whether you use an external or internal UART. "

to which I'd reply that the UART used for the debugging process probably doesn't need an interrupt at all, since the only program that uses it is the debug monitor. When it needs an interrupt, that one has to be chosen so it doesn't interfere with the target application. It mustn't use resources that the target might need.

You see, things look pretty different from our quite different situations. I think you get into the position of assuming that someone, anyone, doing something differently than you would do them is WRONG. I don't believe that. That's why I jump on you every time you tell someone they shouldn't use the i8255, though I wouldn't do it unless the thing were already on a board, or, that they should use your favorite MCU, which is seldom what the person making the inquiry wants to do. Now, I don't think disagreement is a bad thing in itself, as it reflects differring views of the situation. I find I get much valuable information from folks with opinions that differ from my own, but its value does depend on why it is that you disagree.

RE