Lpc2000

Hi Folks,
    I am very new to the lpc2xxx family (although I am competent at PICs) so I am looking 
at what other people do with the peripherals. My current line of investigation is the UARTs, 
which are described as "550-compatible".
Of course I want everything i.e. interrupt-driven and externally-buffered serial input and 
output, but I don't seem to be having much success at finding example source code that 
makes good use of the hardware uart transmit buffer. Can people suggest where to look / 
what terms to google with?

I have seen (for example) the drivers posted by sashi_ono but (as I understand it) they 
don't use the hardware transmit buffer. Perhaps this is related to my PIC background, 
where I previously had to scrape every last cycle of performance out of the hardware but 
that's unnecessary in the luxurious arm environment.

What's the problem with that code? I'm in no position to criticise - I assume this is solid, 
working code (more than anything I've produced) but I reckon it doesn't use the 16-level 
FIFO on transmit. This is a low-level hardware issue because the THREEmpty interrupt 
occurs when the FIFO is _empty_ - not when there's space to put more characters into it. 
So you could - assuming there are that many characters in the external transmit buffer - 
pump 16 characters into U0THR in response to a THREEmpty interrupt, and thereby save 
up to 15/16 ISR call overheads.

Is this worth the extra effort for an arm? It was often done in the days of the PC. The ISR 
call overhead is not very great in terms of cycles, and it might only be noticed at high baud 
rates.

What do people think? I invite comments on this point.

Regards,
Danish