下面是在DNW工具中打印出来的信息：

EP0 Interrupt
INFO : IsrUsbd : Interrupt occurred
INFO : s2440INT->SRCPND = 0x2000008
INFO : s2440INT->INTMSK = 0xFDF7FFFF
INFO : s2440INT->INTPND = 0x2000000
INFO : s2440PWR->CLKCON = 0xFFFF0
INFO : pUSBCtrlAddr = 0xB1200140
INFO : pUSBCtrlAddr->EIER.ep0_int_en = 0x1
INFO : pUSBCtrlAddr->EIER.ep1_int_en = 0x1
INFO : pUSBCtrlAddr->EIER.ep2_int_en = 0x1
INFO : pUSBCtrlAddr->EIER.ep3_int_en = 0x1
INFO : pUSBCtrlAddr->EIER.ep4_int_en = 0x1
INFO : pUSBCtrlAddr->EIR.ep0_int = 0x1
INFO : pUSBCtrlAddr->EIR.ep1_int = 0x0
INFO : pUSBCtrlAddr->EIR.ep2_int = 0x0
INFO : pUSBCtrlAddr->EIR.ep3_int = 0x0
INFO : pUSBCtrlAddr->EIR.ep4_int = 0x0

EP0 Interrupt
USB host is connected. Waiting a download.
INFO : IsrUsbd : Interrupt occurred
INFO : s2440INT->SRCPND = 0x2000008
INFO : s2440INT->INTMSK = 0xFDF7FFFF
INFO : s2440INT->INTPND = 0x2000000
INFO : s2440PWR->CLKCON = 0xFFFF0
INFO : pUSBCtrlAddr = 0xB1200140
INFO : pUSBCtrlAddr->EIER.ep0_int_en = 0x1
INFO : pUSBCtrlAddr->EIER.ep1_int_en = 0x1
INFO : pUSBCtrlAddr->EIER.ep2_int_en = 0x1
INFO : pUSBCtrlAddr->EIER.ep3_int_en = 0x1
INFO : pUSBCtrlAddr->EIER.ep4_int_en = 0x1
INFO : pUSBCtrlAddr->EIR.ep0_int = 0x1
INFO : pUSBCtrlAddr->EIR.ep1_int = 0x0
INFO : pUSBCtrlAddr->EIR.ep2_int = 0x0
INFO : pUSBCtrlAddr->EIR.ep3_int = 0x0
INFO : pUSBCtrlAddr->EIR.ep4_int = 0x0

测试结果：

Ethernet Boot Loader Configuration:

0) IP address: 192.168.1.1
1) Subnet mask: 255.255.255.0
2) DHCP: Disabled
3) Boot delay: 16 seconds
4) Reset to factory default configuration
5) Startup image: DOWNLOAD NEW
6) Program disk image into SmartMedia card: Disabled
7) Program DM9000 MAC address (20:04:09:18:00:07)
8) Kernel Debugger: ENABLED
9) Format Boot Media for BinFS
B) Mark Bad Block at Reserved Block
D) Download image now(USE TFTP)
E) Erase Reserved Block
F) Low-level format the Smart Media card
L) LAUNCH existing Boot Media image
R) Read Configuration
U) Download image now(USE USB)
W) Write Configuration Right Now

Enter your selection: u
System ready!
Preparing for download...
USB host is not connected yet.
USB host is connected. Waiting a download.
OEMPreDownload::USB host is Connected.
USB host is connected. Waiting a download.

休息一下，，，喝了一杯茶。。。嘿嘿，最后发现启动代码的汇编部分，没有进行中断的堆栈初始化。。哈哈。。。