Control Data Cyber 170 State Hardware Reference Manual page 200

Instruction Lookahead Purge Control
Illegal
Instructions
An instruction is illegal when it has an illegal operating code, an illegal
operating parameter, or when it is positioned so that it begins in one
instruction word and extends into the next instruction word. In the CYBER 170
job mode, illegal instructions cause an exchange to the CYBER 170 monitor
mode.
In the CYBER 170 monitor mode, illegal instructions cause a
jump to
executive state. The CP stops. CP illegal instructions are:
011, 012, 013, 464, 465, 466, 467 if they do not begin at parcel 0.
011, 012, 014, 015 if the UEM enable flag in the flag register of the CYBER
170 exchange package is clear.
Any 30-bit instruction that begins at parcel 3 .