The Or1ksim MMU ustates parameter (in sections dmmu and immu) is given a default value of 0 (which appears to mean "do nothing with this parameter").
However if set, the parameter is constrained to take values of 2, 3 or 4.
This should be changed, either to allow 0 as an explicit value, or (if 0 is not really a suitable value) to set a suitable default of 2, 3 or 4.
Fixed in Or1ksim 0.3.0rc1. The default value is now 2