The D-Link DSL-2600U model has different hardware variants (e.g. Z1 and Z2). If you downloaded the wrong firmware variant from the D-Link support website and updated your router and the router won't boot anymore, it's possible to bring this old router once again to life.
Preparation
You need a USB to Serial adapter (mine is Prolific PL2303). Open the router case and connect the GND adapter's pin to the GND port on the router's board, Tx to the Rx and Rx to the Tx.
Setting up the environment
Make sure that you've installed the adapter drivers and connected the adapter to your system's USB port. Download TeraTerm and run it. In the application, open a new serial connection to the router, and from the Setup > Serial Port menu, change the "Baud rate / Speed" to 115200.
You should see the following output on the console when turning the router on.
Bootbase Version: VTC_SPI1.26 | 2012/12/26 16:00:00 RAM: Size = 16384 Kbytes Found SPI Flash 2MiB Winbond W25Q16 at 0xbfc00000
Flashing the chipset
Turn off the router, press and hold the reset button and then press the power button to turn the device on. If you see the following output on the console, you've successfully booted into the SoC bootloader.
RT63365 at Tue May 8 19:47:16 CST 2012 version 0.8 Memory size 16MB HWCONF=04005d00 DRAM Mode=00000000 MCC1=00000000 Search PHY addr and found PHY addr=0 done
On the console, press the x key and from the File > Transfer > XMODEM > Send... menu, send the recovery.img file to the router. The router will reboot to the recovery image after the upload process is done.
done CCreceived len=0000bb00 jump to 80008000 len=00000000 RT63365 at Thu Apr 2 18:14:49 MSK 2015 version 1.1 Memory size 16MB flash base: b0000000 Found SPI Flash 2MiB Winbond W25Q16 at 0xb0000000 cmd >
You can type help to see the available commands.
Now it's time to rewrite the flash chip. Type the xmdm 80300000 200000 command and hit enter. After that, from the File > Transfer > XMODEM > Send... menu, upload the flash.bin (firmware version is 1.08 and it's for the Z2 variant—I don't have the Z1 variant) file to the router volatile memory.
cmd > xmdm 80300000 200000 CCCreceived len=200000
Then, you can write the uploaded flash file with the flash 0 80300000 200000 command to the chipset.
cmd > flash 0 80300000 200000 Write to flash from 80300000 to 0 with 200000 bytes erase addr=0 size=10000 erase addr=10000 size=10000 erase addr=20000 size=10000 erase addr=30000 size=10000 erase addr=40000 size=10000 erase addr=50000 size=10000 erase addr=60000 size=10000 erase addr=70000 size=10000 erase addr=80000 size=10000 erase addr=90000 size=10000 erase addr=a0000 size=10000 erase addr=b0000 size=10000 erase addr=c0000 size=10000 erase addr=d0000 size=10000 erase addr=e0000 size=10000 erase addr=f0000 size=10000 erase addr=100000 size=10000 erase addr=110000 size=10000 erase addr=120000 size=10000 erase addr=130000 size=10000 erase addr=140000 size=10000 erase addr=150000 size=10000 erase addr=160000 size=10000 erase addr=170000 size=10000 erase addr=180000 size=10000 erase addr=190000 size=10000 erase addr=1a0000 size=10000 erase addr=1b0000 size=10000 erase addr=1c0000 size=10000 erase addr=1d0000 size=10000 erase addr=1e0000 size=10000 erase addr=1f0000 size=10000 program from 0 to 200000 ................................................................
All done! Just reboot the router, and now you should see the complete bootlog on the console.
Bootbase Version: VTC_SPI1.26 | 2012/12/26 16:00:00 RAM: Size = 16384 Kbytes Found SPI Flash 2MiB Winbond W25Q16 at 0xbfc00000 SPI Flash Quad Enable Turn off Quad Mode RAS Version: v1.08 System ID: $2.12.108.1(G04.BZ.4)3.20.21.0| 2013/11/28 20131128_v003 | 2013/11/28 Press any key to enter debug mode within 3 seconds. ...........
⚠️ Warning
The previous stored configurations on the router should be cleared. To do that, plug the LAN cable into the router, head to the http://192.168.1.1 page, and reset the configurations to the factory defaults.
🚩 Note
You can view the debug console help menu with theATHEcommand.ATHE ======= Debug Command Listing ======= AT just answer OK ATHE print help ATBAx change baudrate. 1:38.4k, 2:19.2k, 3:9.6k 4:57.6k 5:115.2k ATENx,(y) set BootExtension Debug Flag (y=password) ATSE show the seed of password generator ATTI(h,m,s) change system time to hour:min:sec or show current time ATDA(y,m,d) change system date to year/month/day or show current date ATDS dump RAS stack ATDT dump Boot Module Common Area ATDUx,y dump memory contents from address x for length y ATRBx display the 8-bit value of address x ATRWx display the 16-bit value of address x ATRLx display the 32-bit value of address x ATGO(x) run program at addr x or boot router ATGR boot router ATGT run Hardware Test Program ATRTw,x,y(,z) RAM test level w, from address x to y (z iterations) ATSH dump manufacturer related data in ROM ATDOx,y download from address x for length y to PC via XMODEM ATTD download router configuration to PC via XMODEM ATUR upload router firmware to flash ROM < press any key to continue > ATLC upload router configuration file to flash ROM ATXSx xmodem select: x=0: CRC mode(default); x=1: checksum mode ATLD Upload Configuration File and Default ROM File to Flash ATCD Convert Running ROM File to Default ROM File into Flash OK