IPC@CHIP Documentation - SC12 @CHIP-RTOS V1.10

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IPC@CHIP Documentation Index
Primary Task Attributes
Two important attributes of each task are task priority and state.
Task Priority
Each task executing under the @Chip-RTOS has a unique internal task priority. This internal task priority is
represented with a 16 bit value, the most significant byte of which is the user task priority which is set at
task creation time or using the RTX_Change_Task_Prio() API (and is visible through the
RTX_Get_Task_State() API). The hidden least significant byte of the task priority is used internally by the
@Chip-RTOS to assign each task at a given user priority a unique priority by appending a sequence
number to the upper byte.
A task is assigned the lowest internal priority of all tasks with the same user priority whenever that task is
appended to the list of tasks at that given user priority. This occurs when:
a) the task is created
b) the task's priority is changed
c) the task's time-slice period times out (see chapter Time-Slicing).
Application program tasks can range in user priority from 3 to 127 (inclusive), where 3 is higher priority.
Generally, user task priorities between 20 and 30 are recommended. This recommendation is based on the
priority assignments of the built-in system tasks. Too high a priority for an application task may block urgent
system tasks: e.g. the Ethernet receiver task.
Task State
In Table 2 below, the possible states and sub-states for @Chip-RTOS tasks are summarized. There are
three primary states: Active, Blocked and Suspended.
State Sub-State Notes and State Transitions
Active Executing Highest priority non-waiting task
Pending In queue ordered by task priority
Blocked Trigger Wait 1 RTX_Restart_Task() → Active
Semaphore Wait 2 RTX_Signal_Sem(), RTX_Release_Sem() →
Active
Event Group Wait 2 RTX_Signal_Events() → Active
Message Exchange Wait 2 RTX_Send_Msg() → Active
Asleep 2 RTX_Wakeup() → Active
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