ucOS的数据结构中最核心的一个数据结构就是任务控制块数据结构，其他的数据类型都是围绕该数据结构展开的，任务切换，代码调度也都是以该数据结构为基础来完成的。认清了该数据结构就了解了ucOS的运行机制。任务控制块数据结构如下：

typedef struct os_tcb {

OS_STK *OSTCBStkPtr; /* Pointer to current top of stack */

#if OS_TASK_CREATE_EXT_EN > 0

void *OSTCBExtPtr; /* Pointer to user definable data for TCB extension */

OS_STK *OSTCBStkBottom; /* Pointer to bottom of stack */

INT32U OSTCBStkSize; /* Size of task stack (in number of stack elements) */

INT16U OSTCBOpt; /* Task options as passed by OSTaskCreateExt() */

INT16U OSTCBId; /* Task ID (0..65535) */

#endif

struct os_tcb *OSTCBNext; /* Pointer to next TCB in the TCB list */

struct os_tcb *OSTCBPrev; /* Pointer to previous TCB in the TCB list */

#if (OS_EVENT_EN) || (OS_FLAG_EN > 0)

OS_EVENT *OSTCBEventPtr; /* Pointer to event control block */

#endif

#if (OS_EVENT_EN) && (OS_EVENT_MULTI_EN > 0)

OS_EVENT **OSTCBEventMultiPtr; /* Pointer to multiple event control blocks */

#endif

#if ((OS_Q_EN > 0) && (OS_MAX_QS > 0)) || (OS_MBOX_EN > 0)

void *OSTCBMsg; /* Message received from OSMboxPost() or OSQPost() */

#endif

#if (OS_FLAG_EN > 0) && (OS_MAX_FLAGS > 0)

#if OS_TASK_DEL_EN > 0

OS_FLAG_NODE *OSTCBFlagNode; /* Pointer to event flag node */

#endif

OS_FLAGS OSTCBFlagsRdy; /* Event flags that made task ready to run */

#endif

INT16U OSTCBDly; /* Nbr ticks to delay task or, timeout waiting for event */

INT8U OSTCBStat; /* Task status */

INT8U OSTCBStatPend; /* Task PEND status */

INT8U OSTCBPrio; /* Task priority (0 == highest) */

INT8U OSTCBX; /* Bit position in group corresponding to task priority */

INT8U OSTCBY; /* Index into ready table corresponding to task priority */

#if OS_LOWEST_PRIO <= 63

INT8U OSTCBBitX; /* Bit mask to access bit position in ready table */

INT8U OSTCBBitY; /* Bit mask to access bit position in ready group */

#else

INT16U OSTCBBitX; /* Bit mask to access bit position in ready table */

INT16U OSTCBBitY; /* Bit mask to access bit position in ready group */

#endif

#if OS_TASK_DEL_EN > 0

INT8U OSTCBDelReq; /* Indicates whether a task needs to delete itself */

#endif

#if OS_TASK_PROFILE_EN > 0

INT32U OSTCBCtxSwCtr; /* Number of time the task was switched in */

INT32U OSTCBCyclesTot; /* Total number of clock cycles the task has been running */

INT32U OSTCBCyclesStart; /* Snapshot of cycle counter at start of task resumption */

OS_STK *OSTCBStkBase; /* Pointer to the beginning of the task stack */

INT32U OSTCBStkUsed; /* Number of bytes used from the stack */

#endif

#if OS_TASK_NAME_SIZE > 1

INT8U OSTCBTaskName[OS_TASK_NAME_SIZE];

#endif

} OS_TCB;

其中

OSTCBStkPtr--任务栈的指针，在任务中使用到的所有零时变量(包括任务切换时需要保存的上下文)都保存在OSTCBStkPtr指向的存储区域

OSTCBExtPtr--任务扩展数据信息指针，目前我理解这一部分主要用于保存任务名字的ASCII码

OSTCBStkBottom--任务栈底指针

OSTCBStkSize--任务栈的大小

OSTCBNext--任务控制块链表中的下一任务指针

OSTCBPrev--任务控制块链表中的上一任务指针

OSTCBEventPtr--任务等待时间指针，该数据结构本身是属于一个事件的，任务也只是属于事件的一个候选资源

OSTCBEventMultiPtr--互斥信号量指针

OSTCBMsg--邮箱指针