[U-Boot] Loading nvram with U-Boot via the serial port

[Alex]

Cable modem, the nvram memory seems to be corrupted.  U-Boot 1.2.0 bootloader is working, I can connect to modem via serial interface, view boot process and upload firmware. I know U-Boot support loading files via the serial port using kermit or y-modem protocols. Can I reflash the NVRAM with U-Boot via the serial  port? I have nvram backup.
I know how to use HyperTerminal in Windows to transfer binary (in "ymodem" mode). I'm not sure what offset address to specify in loady command, and what are the next steps after the upload is complete (erase the NVRAM before copying new, reset, etc). 

SPI Flash memory structure, from printenv:

7 cmdlinepart partitions found on MTD device spansion
partitions[0] = {.name = U-Boot, .offset = 0x00000000,.size = 0x00020000 (128K) }
partitions[1] = {.name = env1, .offset = 0x00020000,.size = 0x00010000 (64K) }
partitions[2] = {.name = env2, .offset = 0x00030000,.size = 0x00010000 (64K) }
partitions[3] = {.name = firmware_101222c, .offset = 0x004a0000,.size = 0x002d0000 (2880K) }
partitions[4] = {.name = nvram, .offset = 0x007b0000,.size = 0x00050000 (320K) }
partitions[5] = {.name = UBFI1, .offset = 0x00040000,.size = 0x003b0000 (3776K) }
partitions[6] = {.name = UBFI2, .offset = 0x003f0000,.size = 0x003b0000 (3776K) }
Creating 7 MTD partitions on "spansion":
0x00000000-0x00020000 : "U-Boot"
0x00020000-0x00030000 : "env1"
0x00030000-0x00040000 : "env2"
0x004a0000-0x00770000 : "firmware_101222c"
0x007b0000-0x00800000 : "nvram"
0x00040000-0x003f0000 : "UBFI1"
0x003f0000-0x007a0000 : "UBFI2"


Can someone give me advice?