PW2 Garbled code in 5.6.1.0.4 jailbreak(serial port)

Hello everyone, i just began to jailbreak my KPW2 (Japanese version, fw5.6.1.0.4) with serial port. But all codes garbled when i restarted the device, and all input didn't work when "Hit any key to stop autoboot" shown up.
I've tried following setting in XShell 5:
115200 bps, 8 data bits, 1 stop bits, no parity, no flow control
115000 bps, 8 data bits, 1 stop bits, no parity, no flow control
115000 bps, 8 data bits, 2 stop bits, no parity, no flow control
But all of them failed.
Terminal encoding is Unicode(UTF-8).
What should i do?

Thanks.