Need help: How do I flash EC.ROM?

[gens]

I'm new to BIOS world, so sorry if I am asking something really trivial.

I'm trying to downgrade my Toshiba Satellite C55-B5202's BIOS from version 5.10 (latest) to 1.70. Since Toshiba's BIOS flash utility doesn't allow downgrading BIOS, I downloaded BIOS flashing utility from AMI website. Also I extracted the following files from Toshiba's .exe file.

  BIOS.ROM (size: 8MB)
  EC.ROM (size: 128KB)

Using AMI's afuwin utility, I was able to flash BIOS.ROM. Not knowing what to do with EC.ROM, I rebooted the computer. I was able to enter BIOS and confirmed that BIOS was indeed downgraded to 1.70 successfully. However, I noticed that EC version still says 5.10 as below.

  System BIOS Verion: 1.70
  EC Version: 5.10

I tried to install Windows 10 anyway, but the installer didn't recognize my hard drive.

So, I created a bootable USB stick with afudos.exe on it and tried to flash EC.ROM part. It tried using /E and /EC options without success. However, I could flash version 5.10 BIOS.ROM using the following command and bring the computer back to the initial state.

  afudos.exe BIOS.ROM /p /b /n /k

So, the computer is not bricked, but my goal is not accomplished. I need to flash version 1.70 EC.ROM on this computer somehow.

I did lots of search in this forum and internet but the only information I could find wat that EC.ROM has to do with Embedded Controller. No one seemed to know how to flash it.

Any help would be appreciated.