I Tftp Upgrade Firmware Version 1255 Download New: Upd

Downloading to RAM is not enough. You must write to flash/ROM:

Or, if the device has a dedicated upgrade command: i tftp upgrade firmware version 1255 download new

erase 0x9f020000 +0x1000000 cp.b 0x80000000 0x9f020000 0x1000000 Downloading to RAM is not enough