[U-Boot-Users] How to do DUART loopback test on MPC8541?

[wylg at sina.com]

hello,all
I'm new to u-boot, now I am working on MPC8541, I use DUART1 as my serial port, I want to do loopback test on DUART1, but it isn't working, so I want to know how to do loopback test on DUART1.Can you help me?
below is my processing steps:
1) set UCLR1=0x00 (close DLAB)
2) set UIER1=0x00 (disable interrupt)
3) set UMCR1=0x12 (allow loopback)
4) set UTHR1=0x5a (sending a char)
5) get the loopback value from URBR1 (but I always get value 0)
best regards
leo

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