Control Data Cyber 170 State Hardware Reference Manual page 44

Registers
RAE Register
The 21-bit UEM reference address (RAE) register loads from CM during the fifth
word of a CYBER 170 exchange sequence. The lower 6 bits of this register are
always 0. An absolute UEM address forms by adding RAE to the relative address,
which is determined by the instruction.
FLE Register
The 24-bit UEM
field length (FLE) register loads from CM during the sixth word
of a CYBER 170 exchange sequence. The lower 6 bits of this register are always
0.
The
FLE
register defines the size of the field in UEM for the program in
execution.
Relative UEM addresses are compared with FLE.
MA Register
The 18-bit monitor address (MA) register loads from CM during the seventh word
of a CYBER 170 exchange sequence. The MA register contains the absolute
starting address of an exchange package that is used when executing a central
exchange jump (013) instruction with the CYBER 170 monitor flag clear or when
honoring a monitor exchange jump to
MA
(262x1 instruction with the CYBER 170
monitor flag clear. For further information, refer to CYBER 170 Exchange Jump
in chapter
5.