;/****************************************Copyright (c)**************************************************
;** Guangzou ZLG-MCU Development Co.,LTD.
;** graduate school
;** http://www.zlgmcu.com
;**
;**--------------File Info-------------------------------------------------------------------------------
;** File Name: IRQ.s
;** Last modified Date: 2004-06-14
;** Last Version: 1.1
;** Descriptions: The irq handle that what allow the interrupt nesting.
;**
;**------------------------------------------------------------------------------------------------------
;** Created By: Chenmingji
;** Created date: 2004-09-17
;** Version: 1.0
;** Descriptions: First version
;**
;**------------------------------------------------------------------------------------------------------
;** Modified by:
;** Modified date:
;** Version:
;** Descriptions:
;**
;********************************************************************************************************/
NoInt EQU 0x80
USR32Mode EQU 0x10
SVC32Mode EQU 0x13
SYS32Mode EQU 0x1f
IRQ32Mode EQU 0x12
FIQ32Mode EQU 0x11
CODE32
AREA IRQ,CODE,READONLY
MACRO
$IRQ_Label HANDLER $IRQ_Exception_Function
EXPORT $IRQ_Label ; The label for exports 输出的标号
IMPORT $IRQ_Exception_Function ; The imported labels 引用的外部标号
$IRQ_Label
SUB LR, LR, #4 ; Calculate the returning address 计算返回地址
STMFD SP!, {R0-R3, R12, LR} ; Protects the task environments 保存任务环境
MRS R3, SPSR ; Protects the status variable 保存状态
STMFD SP, {R3,LR}^ ; Protects SPSR and SP in user status, Notice: DO NOT write back.保存SPSR和用户状态的SP,注意不能回写
; If the SP is written back, it should be adjusted to its appropriate value later.如果回写的是用户的SP，所以后面要调整SP
NOP
SUB SP, SP, #4*2
MSR CPSR_c, #(NoInt | SYS32Mode) ; Switch to the System Mode 切换到系统模式
BL $IRQ_Exception_Function ; call the C interrupt handler funtion 调用c语言的中断处理程序
MSR CPSR_c, #(NoInt | IRQ32Mode) ; Switch bak to IRQ mode 切换回irq模式
LDMFD SP, {R3,LR}^ ; Recover SPSR and SP in user status, Notic: DO NOT write back. 恢复SPSR和用户状态的SP,注意不能回写
; If the SP is written back, it should be adjusted to its appropriate value later.如果回写的是用户的SP，所以后面要调整SP
MSR SPSR_cxsf, R3
ADD SP, SP, #4*2 ;
LDMFD SP!, {R0-R3, R12, PC}^ ;
MEND
;/* 以下添加中断句柄，用户根据实际情况改变 */
;/* Add interrupt handler here，user could change it as needed */
;Timer0_Handler HANDLER Timer0
END
;/*********************************************************************************************************
;** End Of File
;********************************************************************************************************/
