OKIDATA DOC-IT3000, Service Manual

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Service Guide DOC-IT3000/4000
Chapter 2 Principles of Operation
Kernel Primitives
The kernel primitives fall into the following categories:
· Kernel Initialization which establishes the kernel operating environment.
· Task Management with primitives to create, manage, and schedule tasks in a
multi-tasking environment. The kernel offers priority scheduling combined with optional
time slice (round robin) scheduling.
· Interrupt Management by immediately switching control to a specified interrupt service
routine when an interrupt occurs. Most of the kernel primitives can be executed direct
from the interrupt service routine.
· Time Management providing one-shot alarm, repetitive alarm and a real-time clock.
Alarms can be reset to implement watchdog timers.
· Memory Management that provides fixed (static) and variable (dynamic) block
allocation.
· Inter-Task Communications and synchronization includes:
- Semaphore used for inter-task signaling and synchronization.
- Binary Semaphores used to ensure mutual exclusion and prevent deadlock.
· Message Queues are queues that can hold any number of messages and are used to
exchange data between tasks.
· Fault Handling that services or corrects faults by the 80960 processor.
Kernel Service Routines
Kernel service routines fall into the following categories:
· Resource Manager
- By allocating memory to different tasks, the Resource Manager manages the printer
engine, scanner engine and the page buffer to guarantee the mutually exclusive access to
these hardware resources. The memory size on the Controller determines the number of
page buffers that can be allocated to each task. For example, if two page buffers are
available, then the scan and print tasks can be processed simultaneously.
· Error Handler
- A set of routines that pass messages back and forth to the Resource Manager to handle
error conditions.
Host-Controller Communications
This section describes how the PC host to Controller communications mechanism works. There
are two major functional modules involved; the TSR module on the PC host and the HOST I/O