• 中断向量表

Exception preTx. The setting of IP speciTes whether an exception vector offset is prepended with Fs
or 0s. In the following description, nnnnn is the offset of the exception vector. See Table 7-1.
0 Exceptions are vectored to the physical address 0x000n_nnnn
1 Exceptions are vectored to the physical address 0xFFFn_nnnn
The reset value of IP is determined by the IIP bit (bit 2) in the hard reset confguration word.

Offset	Exception	Description
0x00000	Reserved
0x00100	System reset interrupt
0x00200	Machine check interrupt
0x00300	DSI	A DSI exception is never generated by hardware, but software may branch to this location because of an data TLB error or miss exception.
0x00400	ISI	An ISI exception is never generated by the hardware, but software may branch to this location because of an implementation-speciTc instruction TLB error exception.
0x00500	External Interrupt
…	…	…

    这个表结合地址映射表可知系统复位的地址是 Socket Flash地址+系统复位偏移地址 = 0xFFF80000 + 0x0100 = 0xFFF80100,即系统通电后,跳到0xFFF80100的位置开始执行程序.

MPC860串口中断过程

    MPC860集成了两个处理块,一个处理块是嵌入的PowerPC核，另一个是通信处理模块（CPM）.通信处理模块有4个SCC和2个SMC,这六个通信口可以通过设置来支持多种协议和通信方式,也可设置为串口UART模式(是通过寄存器GSMR或SMCMR),功能和中断的定义和通常的串口定义基本是一致的在寄存器SCCM/SCCE的位14和位15定义了在何种情况下产生硬件中断.

    根据MPC860中SCC UART Event Register(SCCE)的位14和位15定义,位14是数据发送中断标志位,位15是数据接收中断标志位,首先设置SCC UART Mask Register(SCCM)的位14和位15为1,使能接受和发送中断.
如果串口收到数据,则产生硬件RX中断,SCCE为15置1,通知系统有数据到达,有相应的中断例程ISR来取数据.

    发送的情况下,数据FIFO为空,产生TX中断,告诉系统发送准备就绪,可以发送,ISR把数据放入FIFO中,发送中断位清零.当发送完毕后,FIFO再为空,再次产生中断,告诉系统发送准备就绪,继续发送.