Most of this Reference Manual and the published descriptions of Orion and its programming techniques are concerned with the normal or Programmers' Mode in which the system operates. When an interruption occurs the Monitor Staticisor (also known as HKFF) is turned on and the computer is thrown into the Monitoring Mode, in which part of the Monitor Program operates; the Monitor Program returns the computer to Programmers' Mode by obeying a 152-instruction. The Monitoring Mode can be thought of as a subsidiary mode of the Programmers' Mode.
The following events occur in Monitoring Mode and not in normal Programmers' Mode.
There is a key-operated switch on the main control panel of the computer which can be used to put the machine into Engineering Mode. In this mode the computer behaves exactly as in the Monitoring Mode described above but with the following exceptions:
The key to operate the switch may be inserted and withdrawn only when the switch is turned to the Normal (Programmers' Mode) position.
The same key-operated switch referred to in Sec. 2.3.2, above, can also be used to put the computer into Engineers' Time-Sharing Mode. The machine then behaves exactly as in normal Programmers' Mode (or Monitoring Mode, since interruptions are allowed) except that the engineers' control keys described above are operative. This mode facilitates maintenance of the time-sharing features of the system.
The information in this Section refers in general to both Orion 1 and Orion 2. Described here are the differences to be noted when reading these sections for Orion 2.
Subsection (d) On Orion 2 the datum point is ignored not cleared.
Subsection (c) On Orion 2 no pulse is lost and so these instructions may be obeyed in these circumstances.