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Software
The System software consists of switched services, administrative, and maintenance
software. This software runs on top of the real-time operating system software.
Switched Services Software
The switched services software provides voice and data call processing. This software
resides in the Call Processor and Memory Circuit Packs (that are collectively referred to as
the Common Control circuitry), and in the 8-bit on-board microprocessors located in the port
and service circuits.
The switched services software uses the operating system to provide a process based,
message passing, execution environment. The operating system scheduler provides scheduling
for the software according to process priority.
Administrative Software
The administrative software provides the control for system rearrangement and change via
the System Administration Terminal (SAT). This software resides in the Memory Circuit
Pack and does the following functions:
● Organizes the translation data for administrable entities in the system in a form
that can be viewed and changed at the System Administration Terminal.
● Tests entered data for consistency with data previously entered in order to avoid
such errors as the assignment of the same extension number to two voice terminals.
An erroneous or inconsistent data entry is disallowed and an error message is
provided.
● Causes the translation data to be downloaded, on command, to an optional Digital
Tape Unit (DTU).
Maintenance Software
The maintenance software provides automatic periodic testing of maintenance objects within
the system as well as consistency tests among the call status tables within the system. In
addition, demand testing is initiated when the system detects a condition requiring a need
for testing. Software tables are provided for storing error records. The records can be
accessed by maintenance personnel via the SAT. A Permanent System Alarm (a serious
error) causes an alarm indicator on the attendant console to light and an error record to be
stored in the error table.
Memory Allocation
The system software, like the hardware, is identified by release and version number. Each
version identifies a particular memory configuration for the release number. Main memory
is located in the Common Control circuitry. The operating system and error log software
resides on the Call Processor circuit pack and the remaining administration and call
processing software is on the Memory circuit pack.
Real-Time Constraints
Real-time constraints are a function of the speed of the common control circuitry and the
traffic load. The switch is designed so that many time-consuming and repetitious functions
are performed by processors in the port and service circuit packs, thus relieving the common
control circuits.
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