in the SiLabs forum someone showed SFR = -n
I have never used such and became curuous. I searched the Keil documentation but could nof find it.
it is defined as SFR so my question still stands is it rerated as unsigned or signed
You need to be careful to flag it as a C51 question - there's nothing in the forum to tell that any more, and C51 questions are very rare.
I agree, the documentation omits this:
http://www.keil.com/support/man/docs/c51/c51_le_sfr.htm
But it wouldn't make sense to have SFRs signed - as that would imply sign extension, etc.