INtime® 3.1 Software - tenAsys

INtime 3.1 Software
• Low-level objects consume only memory. Therefore, only the amount of system
memory controls how many low-level objects can be present at a given time.
The RT kernel provides these objects. Each object is discussed on the indicated page:
Object Description Page
Threads Do the work of the system and respond to interrupts and events. 30
Processes Environments where threads do their work. 30
Exchange objects Used by threads to pass information. 34
Mailboxes Used by threads to pass objects and data. INtime software includes 35
both object and data mailboxes.
Semaphores Used by threads to synchronize. 36
Regions Used by threads to provide mutual exclusion. 37
Ports
Used by threads to synchronize operations, pass messages, and 38
access INtime services.
Dynamic memory Addressable blocks of memory that threads can use for any
purpose.
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Note
For detailed information about RT kernel objects, how they operate, and system calls associated
with each object, see INtime Help.
Threads
Threads, or threads of execution, are the active, code-executing objects in a system.
Threads typically respond to external interrupts or internal events. External interrupts
include events such as a keystroke, a system clock tick, or any other hardware-based
event. Internal events include events such as the arrival of a message at a mailbox.
Threads have both a priority and an execution state, whether the thread is running or not.
There are system calls to create and delete threads, view and manipulate a thread’s
priority, control thread readiness, and obtain thread handles. For a list and description
of these system calls, see Appendix A, “INtime software system calls”.
Processes
A process is an RT kernel object that contains threads and all their needed resources.
Processes make up your INtime applications. The RT kernel processes have these
characteristics:
• Cannot make system calls; they are passive.
• May include one or more threads.
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