AM1808: UART Boot

few year ago

I was able to do UART boot on SBC 8018 using AM1808 using TeraTerm send file viaModem X

But Now I cannot findits stuff on my PC

I really appreciate your help in doing so

1. How to set UART boot with pin setting hi / lo
2. How to config uboot for UART boot 
3. What file used for UART boot 
4. What correct sequence for UART boot =order of  file if multi boot file
5. What tool used on Ubuntu for UART boot 

Thnaks in advanced your help

DuyKy