threadx操作系统_threadx usb_threadx缺点(2)

IMPORT _tx_thread_fiq_context_save

IMPORT _tx_thread_fiq_context_restore

IF :DEF:TX_ENABLE_IRQ_NESTING

IMPORT _tx_thread_irq_nesting_start

IMPORT _tx_thread_irq_nesting_end

ENDIF

IF :DEF:TX_ENABLE_FIQ_NESTING

IMPORT _tx_thread_fiq_nesting_start

IMPORT _tx_thread_fiq_nesting_end

ENDIF

/*

上面以_tx_thread_*开头的函数，是由theadx OS提供的，主要用在进行中断处理时，保存中断的上下文，便于中断返回时

能够继续执行.以下内容来自ThreadXUserGuide.pdf

Like other ThreadX interrupt service routines, the low-level handler must

call _tx_thread_context_save before calling the driver ISR. After the driver ISR returns, the

low-level handler must call _tx_thread_context_restore.

The following small code segment is typical of most ThreadX managed ISRs. In most cases, this processing is in assembly language.

_application_ISR_vector_entry:

; Save context and prepare for

; ThreadX use by calling the ISR

; entry function.

CALL __tx_thread_context_save

; The ISR can now call ThreadX

; services and its own C functions

; When the ISR is finished, context

; is restored (or thread preemption)

; by calling the context restore

; function. Control does not return!

JUMP __tx_thread_context_restore

上面的英文描述，与实例代码式大致相同

*/

IMPORT myIrqHander

;

;

AREA ||.text||, CODE, READONLY

;

;

EXPORT _irq_handler

EXPORT __tx_irq_processing_return

_irq_handler

;

; /* Jump to context save to save system context. */

B _tx_thread_context_save

__tx_irq_processing_return

;

; /* At this point execution is still in the IRQ mode. The CPSR, point of

; interrupt, and all C scratch registers are available for use. In

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