Merge pull request #104 from riscv/issue/100

encoding clarification for MTT implicit accesses

chapter4.adoc

@@ -336,7 +336,8 @@ translation, but excluding implicit MTT checker accesses to MTT structures. Data
 in M-mode when the MPRV bit in mstatus is set and the MPP field in mstatus contains S
 or U are subject to MTT checks. MTT checker accesses to MTT structures are to be
 treated as implicit M-mode accesses and are subject to PMP/Smepmp and
-IOPMP checks. The MTT checker indexes the MTT using the
+IOPMP checks. Implicit accesses to the MTT are governed by `mstatus.MBE` control
+for RV64 and `mstatush.MBE` control for RV32. The MTT checker indexes the MTT using the
 physical address of the access to lookup and enforce the access permissions.
 A mismatch of the access type and the access permissions specified in the
 MTT entry that applies to the accessed region is reported as a trap to the