Data General AViiON 4600 Series, Customer Documentation

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B-1
014–002091
Appendix B
Using the System Control Monitor
The System Control Monitor (SCM) manages and tests your computer at powerup and
maintains control until the operating system or other system software takes over.
Whenever your system software halts, the SCM resumes control. The SCM consists of
microprograms stored in programmable read-only memory (PROM); these
PROM-based programs are part of your computer hardware (often called
microcode
or firmware ).
The SCM provides a command interpreter and several interactive menus. You can use
SCM commands and menu items to view or change system configuration parameters,
control program flow, debug programs, and boot system software.
Chapter 5 in this manual explains how to use the SCM menus to set or change your
system configuration parameters. This appendix describes basic SCM commands you
can use to boot, program, and debug your system. Refer to
AViiON

4600 Systems
and AViiON 530 Workstations: Programming System Control and I/O Registers for a
description of additional SCM functions not described in this manual.
Getting to the SCM
You can tell you are in the SCM when you see its command interpreter prompt. You'll
only see the SCM prompt when your operating system is completely shut down and the
job processor (or CPU, Central Processing Unit) is halted. The default SCM prompt
appears as follows:
SCM>
If you have a multiprocessor model, all processors must be halted before you see the
SCM prompt. Your default SCM prompt indicates the currently attached job processor,
as follows:
Jp#n/SCM>
You can use the SCM to load, start, modify, control, or halt programs, but the SCM
never runs at the same time as system software. During normal operation, you access
the SCM only when system software encounters a problem it cannot handle while
running.
Your computer displays the SCM command interpreter prompt under the following
circumstances:
•
The SCM controls powerup testing and then brings up your system software
through an automatic boot sequence. You enter the SCM if a diagnostic test fails or
if the automatic boot sequence does not complete successfully.