pdc test project 0 ok

try usart pdc function. the very 1st project: pdc0tx is ok.

pdc usage is simple:

Whenever TX function is enabled (in US_CR)
set US_TCR a value, then PDC start send out US_TCR count data , from the address started from US_TPR.

and US_TCR will decrease on sending, when it reach 0, means all data has been send out. you can prepare
another frame to send.

and the test loop:

while( !pdc0_ready())
.....waitcount++;

find...
send 100 char out, wait count=44891(ICE) 23047(Flash)
send 200 char out, wait count=90641(ICE) 46542(Flash)

(by Multi-ICE)