OKIDATA DOC-IT3000, Service Manual

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Service Guide DOC-IT3000/4000
Chapter 2 Principles of Operation
2.5.05 Software Functional Components
Multi-Tasking Kernel
The heart of the DOC-IT 3000/4000 system is the Multi-Tasking Kernel (MTK). This kernel permits
multiple system functions to run concurrently, providing both a hardware and software interface as
well as services to the Doc-It control modules. The modules include Printer Emulations, Scan,
Facsimile and Copy functions.
All of the tasks running on the Controller are scheduled based on their priority. In some cases,
when two tasks share the same priority number, their scheduling is determined by a time slice
allocation. The front panel task and printer emulations, for example, use time slice allocation for
scheduling because they use the same priority number.
Tasks Purpose Priority
Host I/O PC-Controller communications 20
Fax Interpret incoming message 30
Run_Fax Outgoing scheduler 40
Prt_Fax Print fax queue 50
Scan Scan control 50
Copy and Print Copy and Print control 53
Front Panel Front Panel control 80
Printer Emulation(s) 80
Note: The smaller the number, the higher the priority.
Because of the task scheduling and priority assignments, background and foreground tasks are
executed simultaneously. However, concurrent operation may be limited by the availability of
hardware resources (the printer engine, scanner engine and memory).