Many ISP support pages from 2008–2012 have been archived. Use web.archive.org to find original .bin files from:
The firmware upgrade process typically involves the following steps: huawei echolife hg520b firmware upgrade download verified
power cycle during the 147-second write cycle. A serial console will show: CFE: Programming flash at 0xbfc20000 -> success Many ISP support pages from 2008–2012 have been archived