Lpc2000

From: Soeren Gust <gust@...>

In terms of increasing UART performance, I agree about not using 
Thumb, especially as the IRQ entry/exit code must be in ARM. I 
also agree with the comment about using structures to gain 
base+offset addressing. 

1) Set up the MAM - major impact
2) Consider x2 PLL
3) Set up the UART FCR register to use the FIFOs by interrupting 
every n characters. This reduces the number of interrupts 
considerably. You have to poll the LSR in the interrupt routine 
to empty the FIFO. Don't worry about missing the last few 
characters, the UART will interrupt after a time if the FIFO is 
part full.
4) You can reduce the interrupt latency by making the IRQ vector 
contain:
  ldr   pc, [ pc, # $-FF0 ]
which reads the vector address directly. There is a slight cost 
in that each ISR needs its own entry/exit code. Note also that 
if you want to nest interrupts, you MUST switch to another mode -
 SVC is the usual one to use.

2106 boards with a USB connection will be available from MPE in 
a few weeks. Software will include an on-chip Forth interpreter, 
evaluation versions of the MPE VFX Forth cross compiler and 
Rowley Crossworks C compiler, and we may even get round to a 
BASIC.

Stephen
--
Stephen Pelc, stephen@...
MicroProcessor Engineering Ltd - More Real, Less Time
133 Hill Lane, Southampton SO15 5AF, England
tel: +44 23 80 631441, fax: +44 23 80 339691
web: http://www.mpeltd.demon.co.uk - free VFX Forth downloads