飞思卡尔MC9S12XS128单片机中断优先级设置简易教程

1、本教程试图用最少的时间教你飞思卡尔XS128单片机的中断优先级设置方法和中断嵌 套的使用，如果是新手请先学习中断的基本使用方法。先来看看XS128 Datasheet中介绍的相关知识，只翻译有用的：Each of the I bit maskable interrupt requests can be assigned to one of seven priority levels supporting a flexible priority scheme. For interrupt requests that are configured to be handled by the CPU,

2、 the priority scheme can be used to implement nested interrupt capability where interrupts from a lower level are automatically blocked if a higher level interrupt is being processed. Interrupt requests configured to be handled by the XGATE module can be nested one level deep.七个中断优先级 Each 1 bit mask

3、able interrupt request has a configurable priority level and can be configured to be handled by either the CPU or the XGATE module2.每一个中断源都有一个可以设置的级别1 bit maskable interrupts can be nested, depending on their priority levels.高优先级中断的可以嵌套低优先级中断After system reset all interrupt requests with a vector ad

4、dress lower than or equal to (vector base + OxOOF2) are enabled, are set up to be handled by the CPU and have a pre-configured priority level of 1. Exceptions to this rule are the non-maskable interrupt requests and the spurious interrupt vector request at (vector base + 0 x0010) which cannot be dis

5、abled, are always handled by the CPU and have a fixed priority levels. A priority level of 0 effectively disables the associated 1 bit maskable interrupt request.复位后可屏蔽中断默认优先级为1If more than one interrupt request is configured to the same interrupt priority level the interrupt request with the higher

6、 vector address wins the prioritization.同一优先级的中断同时触发时，高地址（中断号较小）的中断先响应注意：高地址中断只能优先响应，但不能嵌套同一优先级低地址的中断下面直接进入正题，看看怎么设置中断优先级:XS128中包括预留的中断一共有128个中断位，如果为每个中断都分配一个优先级寄 存器的话会非常浪费资源，因此飞思卡尔公司想出了这样一种办法：把128个中断分为16 个组，每组8个中断。每次设置中断时，先把需要的组别告诉某个寄存器，再设置8个中 断优先寄存器的某一个，这样只需9个寄存器即可完成中断的设置。分组的规则是这样的：中断地址位7到位4相同的中断为

7、一组，比如MC9SX128.h中#def i ne#def i ne#def i ne#def i ne#def i ne#def i ne#def i ne#def i neVReserved23VatdOVsc i 1VsciOVsp i 0Vtimpa i eVtimpaaovfVtimovfOxOOOOFffB?)OxOOOOFFD0 x0000FFD4OxOOOOFHD1DCOxOOOOFFOxOOOOFFOxOOOOFFOxOOOOFF这些中断的位7到位3都为D，他们就被分成了一组。0F正好16个组。INT_CFADDR就是上面说到的用来设置组别的寄存器：4.3.2.3Interr

8、upt Request Configuration Address Register (INT_CFADDR)Address: 0 x012776543210INT_CFADDR7:4000000010000Unimplemented or ReservedFigure 4-5. Interrupt Configuration Address Register (INT_CFADDR)我们需要设置某个组别的中断时，只要写入最后8位地址就行了，比如设置SCI0的中断优 先级，就写入0 xD0。#define VsciO0 x0000FFD6设置好组别之后，我们就要该组中相应的中断进行设置，设置中

9、断的寄存器为4.3.2.4Interrupt Request Configuration Data Registers (INT_CFDATA0-7)这其实是一组寄存器，一共有8个，每个都代表中断组中的一个中断。对应规则是这 样的：中断地址的低四位除以2比如还是SCI0，低四位是6，除以二就是3,那么我们就需要设置INT_CFDATA3往INT_CFDATAx中写入07就能设置相应的中断优先级了拿我本次比赛的程序来举个例子：我们的程序中需要3个中断：PIT0,PORTH,SCI0。PIT0 定时检测传感器数值，PORTH连接干簧管进行起跑线检测，SCI0接收上位机指令实现急 停等功能。因此中断

10、优先级要SCI0PORTHPIT0。我们先要从头文件中找出相应中断的地址：#defi ne Vp i tO0 x0000FF7A#def i ne VporthOxOOOOFFCC#def i ne Vsc i 00 x0000FFD6PIT0【7:4】位为7,选择中断组:INT CFADDR=0 x70;【3:0】为A, A/2=5，设置为第5优先级那么 INT CFDATA5=5;porth【7:4】位为C，选择中断组：INT CFADDR=0 xC0;【3:0】为C, C/2=6，设置为第6优先级那么INT CFDATA6=6;Sci0【7:4】位为D，选择中断组：INT CFADDR=0 xD0;【3:0】为6, 6/2=3，设置为第7优先级那么INT CFDATA3=7;最终程序为：void Interrupt_Priority_Set(void)INT CFADDR=0 x70;INT CFDATA5=0 x05;INT CFADDR=0 xC0;INT CFDATA6=0 x06;INT CFADDR=0 xD0;INT CFDATA3=0 x07;还要注意一点，如果要实现中断嵌套，需要在低级中断中再开一次总中断，比如/PHD中断，干簧管检测用VO i d i nterrupt 25 PortH_lNTSvr(void) Egb I e In