When U-boot prints "Hit any key to stop autoboot: 10", enterring many key and many times, it still boots after 10 seconds. What might be the reason? Thank you.
The most common case for such issues IMHO is a bad USB<->UART converter on the host PC, assuming you are using one.
Most cheap ones are flaky and may or may not work reliably at rates higher than 9600.
A good indication if you have a cheap one or not is to see if keeps the COM port setting when removed from one USB port and plugged into another, and if it is designed by spec to handle rates up to ~1Mbps. If it enumerates again and sets up a different COM port, or if kbps is the fastest the spec says it can do, then you may want to look for a better one.
A setup with PuTTY and a good USB<->UART converter is absolutely reliable.
And Windows Hyperterminal is used here with 115200-8-N-1.
By the way, you mentioned Putty, how to set the "flow control"？ There is no "hardware" option for this, I tried "XON/XOFF", there is no response.
Regarding the driver, I had my Win 7 setup discover the correct FTDI driver, so I can’t comment on the FTDI drivers for download that you are referring to.
As for HyperTerminal, I never had a single positive experience with it, so I don’t use it. I have used TeraTerm in the past and currently use mostly Putty as it serves my needs well.
With regards to flow control, I left it as XON/XOFF in my settings, which is ok for my needs.
You never mentioned which board or setup you are using as target. You may want to check a different cable or the electrical signals on the target just to be sure that the host UART bits actually get to the target.
After booting can you able to access the console (i.e) typing some letters, if not check your Tx and Rx connection of your debug UART, there may be some loose conection or it may not be connected
No, cannot type in any letter. So there is connection issue in Tx of console? and no problem with Rx as there is log printed. How to fix? This is mini USB UART on TWR-P1025.
For temporary solution to check whether it is working or not you can take a direct wire connection of debug uart's (Rx, Tx and Gnd) from any resistor point or any other possible points from the board and connect that to DB9 Female connector, from the DB9 Female use USB to Serial converter, connect it to PC and check with minicom