在最近的工程中，需要用到PS/2键盘和鼠标作为控制输入，所以在网上找了一些相关的资料，内容很丰富，看来已经有很多人做过了这方面的编程。本篇Blog算是实践总结，为以后的开发积累一些基础知识。
MicroBlaze支持重启（reset）,中断（ interrupt）, 暂停（break）和异常（ exception）。这里粗略的介绍：
* reset
当外部按键发出reset信号或者XMD通过MDM（MicroBlaze Debug module）发出reset信号，这些信号都会被proc_sys_reset模块接收，然后该模块产生一个16周期长的高电平信号至 MicroBlaze的MB_RESET管脚。MicroBlaze响应reset, PC 寄存器指向0x0地址，依照向量表中代码执行。
* exception
异常是MicroBlaze对内部运行发生错误的情况发做出的响应，这些情况包括：非法指令，指令和数据总线错误和未对齐的访问(unaligned access)。如除0操作，非法操作码异常，数据总线异常等。
* break
break 分为software break和hardware break。hardware break，这时MDM模块的输出端口Ext_BRK和Ext_NM_BRK跟MicroBlaze对应的输入端口相连。一旦break响应，暂停返回地址（break return address）自动装入R16寄存器中。而software break通过brk和brki指令来完成。
* interrupt
MicroBlaze 只支持一个外部中断源（连接于Interrupt 端口），所以需要多个中断输入的话，就得添加中断控制器(xps_intc)了。只有当机器状态寄存器(Machine Status Register,MSR)中的中断使能位（interrupt enable）置'1'，MicroBlaze才能响应中断。MicroBlaze响应中断，PC指向中断向量(地址：0x10)，R14存储了中断返回地址。
注：具体细节问题，请见参考1。
注：该表格来自于MicroBlaze参考手册，见参考1
下面具体介绍如何对MicroBlaze进行中断编程。
1. 中断信号的物理连接
system.mhs文件定义了物理硬件的相关信息，包括总线架构、外围设备、处理器、系统内部信号互连和地址空间等。所以这里就通过MHS定义文件给出关于中断信号互连的信息。
当然MicroBlaze的中断输入，可以配置成电平触发或者边沿触发，在配置MicroBlaze的GUI或者在MicroBlaze.mpd中通过设置 C_INTERRUPT_IS_EDGE ，C_EDGE_IS_POSITIVE来完成对中断的触发的配置。
BEGIN microblaze
. . .
PORT MB_RESET = mb_reset
PORT Interrupt = Interrupt
END
BEGIN xps_uartlite
. . .
PORT Interrupt = RS232_Uart_1_Interrupt
END
BEGIN xps_intc
. . .
PORT Irq = Interrupt
PORT Intr = RS232_Uart_1_Interrupt&plb_ps2_controller_0_IP2INTC_Irpt
END
BEGIN plb_ps2_controller
. . .
PORT IP2INTC_Irpt = plb_ps2_controller_0_IP2INTC_Irpt
PORT mouse_clk = plb_ps2_controller_0_mouse_clk
PORT mouse_data = plb_ps2_controller_0_mouse_data
PORT key_clk = plb_ps2_controller_0_key_clk
PORT key_data = plb_ps2_controller_0_key_data
END
2. EDK提供的驱动以及相关函数的介绍
void microblaze_enable_interrupts(void)
该函数使MicroBlaze可以响应中断，即MSR中的“interrupt enable”位置’1’;
void microblaze_disable_interrupts(void)
该函数使MicroBlaze不能响应中断，即MSR中的“interrupt enable”位置 ’0’;
这几个函数都定义包含在$EDK_project/microblaze_0/include/mb_interface.h
头文件中
XIntc_Initialize(&InterruptController, (Xuint16)INTC_DEVICE_ID);
该函数用于初始化中断控制器，主要包括初始化XIntc的结构体，初始化向量列表，以及所有中断源输入禁用，中断输出禁用。
int XIntc_Connect(XIntc * InstancePtr, u8 Id,
XInterruptHandler Handler, void *CallBackRef)
中断源的标示和相关中断处理程序的连接。
XIntc_Start(XIntcInstancePtr, XIN_REAL_MODE);
该函数使得中断控制器输出的中断信号启用。XIN_REAL_MODE 意思是只允许硬件中断(hardware interrupt)
void XIntc_Enable(XIntc * InstancePtr, u8 Id)
该函数使得对应ID的中断源输入启用
这几个函数定义在$EDK_project/microblaze_0/libsrc/intc_v1_11_a/src/xintc.c
需要包含的头文件：xintc.h
3. C语言编程实例
/*
*Date 2010-12-27
*author Qi Yao
*decription main function code for interrupt program
* such as timer or keyboard and mouse interrupt.
*/
/* FPGA includes */
#include /* for printf */
#include /* for usleep */
#include "xparameters.h"
#include "xutil.h"
#include "xintc.h"
#include "plb_ps2_controller.h"
#include "mb_interface.h"
#define INTC_DEVICE_ID XPAR_INTC_0_DEVICE_ID
int init_input(void);
XStatus SetUpInterruptSystem(XIntc *XIntcInstancePtr);
static XIntc InterruptController;/*Instance of the Interrupt Control*/
/**
* Input interrupt handler
*/
void PS2_InterruptHandler(void *CallbackRef)
{
u32 mouse_state, keybd_state, flags;
Xuint32 baseaddr = (Xuint32) XPAR_PLB_PS2_CONTROLLER_0_BASEADDR;
/* read information from device registers */
keybd_state = ((u32 *)baseaddr)[0];
mouse_state = ((u32 *)baseaddr)[1];
flags = PLB_PS2_CONTROLLER_mReadReg(baseaddr, PLB_PS2_CONTROLLER_INTR_IPISR_OFFSET);
if (flags & EVENT_FROM_MOUSE)
/*mouse event handler*/
handle_mouse_event(mouse_state);
if (flags & EVENT_FROM_KEYBD)
/*keyboard event handler*/
handle_keybd_event(keybd_state);
/* clear interrupt flags in PS/2 controller */
PLB_PS2_CONTROLLER_mWriteReg(baseaddr, PLB_PS2_CONTROLLER_INTR_IPISR_OFFSET, flags);
}
XStatus init_input(void)
{
XStatus Status;
Xuint32 baseaddr = (Xuint32) XPAR_PLB_PS2_CONTROLLER_0_BASEADDR;
/* initialize PS/2 interrupts */
PLB_PS2_CONTROLLER_mWriteReg(baseaddr, PLB_PS2_CONTROLLER_INTR_DIER_OFFSET, 0);
PLB_PS2_CONTROLLER_mWriteReg(baseaddr, PLB_PS2_CONTROLLER_INTR_DGIER_OFFSET, 0xFFFFFFFF);
PLB_PS2_CONTROLLER_mWriteReg(baseaddr, PLB_PS2_CONTROLLER_INTR_IPIER_OFFSET, 0xFFFFFFFF);
PLB_PS2_CONTROLLER_mWriteReg(baseaddr, PLB_PS2_CONTROLLER_INTR_IPISR_OFFSET, 0);
/* initialize Interrupt controller */
Status = XIntc_Initialize(&InterruptController, (Xuint16)INTC_DEVICE_ID);
if (Status != XST_SUCCESS)
{ return XST_FAILURE; }
Status = XIntc_SelfTest(&InterruptController);
if (Status != XST_SUCCESS)
{ return XST_FAILURE; }
/*
* Connect a device driver handler that will be called when an interrupt
* for the device occurs, the device driver handler performs the specific
* interrupt processing for the device
*/
Status = XIntc_Connect(XIntcInstancePtr, XPAR_XPS_INTC_0_PLB_PS2_CONTROLLER_0_IP2INTC_IRPT_INTR,
(XInterruptHandler)PS2_InterruptHandler,
(void *)0);
if (Status != XST_SUCCESS)
{ return XST_FAILURE;}
/*
* Start the interrupt controller such that interrupts are enabled for
* all devices that cause interrupts, specify simulation mode so that
* an interrupt can be caused by software rather than a real hardware
* interrupt
*/
Status = XIntc_Start(XIntcInstancePtr, XIN_REAL_MODE);
if (Status != XST_SUCCESS)
{
return XST_FAILURE;
}
/*
* Enable the interrupt for the device and then cause (simulate) an
* interrupt so the handlers will be called
*/
XIntc_Enable(XIntcInstancePtr, XPAR_XPS_INTC_0_PLB_PS2_CONTROLLER_0_IP2INTC_IRPT_INTR);
/*
* Enable the Interrupts for the MicroBlaze Processor
*/
microblaze_enable_interrupts();
return XST_SUCCESS;
}
int main(void){
/*Initialization*/
init_input();
/*wait for interrupt*/
while(1);
return 1;
}
4. 汇编代码详解
使用mb-objdump工具对实例进行了反汇编，想看看到底是个什么情况
Disassembly of section .vectors.reset:
00000000 <_start>:
0: b0009000 imm -28672
4: b8080000 brai 0 #main()程序起始地址是0x90000000
Disassembly of section .vectors.sw_exception:
00000008 <_vector_sw_exception>:
8: b0009000 imm -28672
c: b8080438 brai 1080
Disassembly of section .vectors.interrupt:
00000010 <_vector_interrupt>:
10: b0009000 imm -28672
14: b8080474 brai 1140 #中断处理程序起始地址是0x90000474
Disassembly of section .vectors.hw_exception:
00000020 <_vector_hw_exception>:
20: b0009000 imm -28672
24: b8080450 brai 1104
90000474 <__interrupt_handler>: #中断处理程序起始地址和汇编代码
90000474: 3021ffb0 addik r1, r1, -80
90000478: f9e10000 swi r15, r1, 0
9000047c: f8610020 swi r3, r1, 32
90000480: f8810024 swi r4, r1, 36
90000484: f8a10028 swi r5, r1, 40
90000488: f8c1002c swi r6, r1, 44
9000048c: f8e10030 swi r7, r1, 48
90000490: f9010034 swi r8, r1, 52
90000494: f9210038 swi r9, r1, 56
90000498: f941003c swi r10, r1, 60
9000049c: f9610040 swi r11, r1, 64
900004a0: f9810044 swi r12, r1, 68
900004a4: fa210048 swi r17, r1, 72
5. 总结
主要描述了MicroBlaze的中断的基本原理，以及编程。
参考文献：
1. MicroBlaze Processor Reference Guide
http://www.xilinx.com/support/documentation/sw_manuals/mb_ref_guide.pdf
2. Using and Creating Interrupt-based Systems
http://www.xilinx.com/support/documentation/application_notes/xapp778.pdf
3. Embedded System Tools Reference Manual
http://www.xilinx.com/support/documentation/sw_manuals/edk10_est_rm.pdf
4. Process System Reset Module
http://www.xilinx.com/support/documentation/ip_documentation/processor_s...
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