OTP wipes backup1 on reset?

HiFive1 Rev B
5
  1. OTP code in the FE310-G002 datasheet is wrong: in my chip it jumps to 00020010 in OTP and executes a lot of code. This code checks first flash memory bytes and pmucause register. In some conditions this code uses backup1 as a counter.
  2. This section is about bootloader in Flash, not OTP
Is there C boot code (source) for RevB02 hardware?