关于ARM2440中断源个数的一点想法

　　S3c2440支持多达36个内部中断源和24个外部中断源，分别使用内部终端屏蔽寄存器INTMSK和外部中断寄存器MSK进行屏蔽控制。其中，外部中断源通过GPIO以复用的方式成为内部中断源的一部分。
　　但是我们清楚，INTMSK是一个32位的寄存器，最多只能支持32中断，它是如何对应这么多中断的呢?
　　首先我们先看INTMSK对应的位。
　　INTERRUPT MASK (INTMSK) REGISTER (Continued)
　　INT_ADC 0 = Service available, 1 = Masked 1
　　INT_RTC 0 = Service available, 1 = Masked 1
　　INT_SPI1 0 = Service available, 1 = Masked 1
　　INT_UART0 0 = Service available, 1 = Masked 1
　　INT_IIC 0 = Service available, 1 = Masked 1
　　INT_USBH 0 = Service available, 1 = Masked 1
　　INT_USBD 0 = Service available, 1 = Masked 1
　　INT_NFCON 0 = Service available, 1 = Masked 1
　　INT_UART1 0 = Service available, 1 = Masked 1
　　INT_SPI0 0 = Service available, 1 = Masked 1
　　INT_SDI 0 = Service available, 1 = Masked 1
　　INT_DMA3 0 = Service available, 1 = Masked 1
　　INT_DMA2 0 = Service available, 1 = Masked 1
　　INT_DMA1 0 = Service available, 1 = Masked 1
　　INT_DMA0 0 = Service available, 1 = Masked 1
　　INT_LCD 0 = Service available, 1 = Masked 1
　　INT_UART2 0 = Service available, 1 = Masked 1
　　INT_TIMER4 0 = Service available, 1 = Masked 1
　　INT_TIMER3 0 = Service available, 1 = Masked 1
　　INT_TIMER2 0 = Service available, 1 = Masked 1
　　INT_TIMER1 0 = Service available, 1 = Masked 1
　　INT_TIMER0 0 = Service available, 1 = Masked 1
　　INT_WDT_AC97 0 = Service available, 1 = Masked 1
　　INT_TICK 0 = Service available, 1 = Masked 1
　　nBATT_FLT 0 = Service available, 1 = Masked 1
　　INT_CAM 0 = Service available, 1 = Masked 1
　　EINT8_23 0 = Service available, 1 = Masked 1
　　EINT4_7 0 = Service available, 1 = Masked 1
　　EINT3 0 = Service available, 1 = Masked 1
　　EINT2 0 = Service available, 1 = Masked 1
　　EINT1 0 = Service available, 1 = Masked 1
　　EINT0 0 = Service available, 1 = Masked 1
　　我们发现INTMSK的第5，6位对应了EINT4_7, EINT8_23，20个外部中断，也就是所，这20个GPIO引脚只能触发这两个中断。
　　但是当中断到来时，我们如果判断是由哪一个GPIO引脚触发的呢?这个时候我们可以通过查询EINTMASK来判断中断源。
　　EINTMASK Bit Description
　　EINT23 0 = enable interrupt 1= masked
　　EINT22 0 = enable interrupt 1= masked
　　EINT21 0 = enable interrupt 1= masked
　　EINT20 0 = enable interrupt 1= masked
　　EINT19 0 = enable interrupt 1= masked
　　EINT18 0 = enable interrupt 1= masked
　　EINT17 0 = enable interrupt 1= masked
　　EINT16 0 = enable interrupt 1= masked
　　EINT15 0 = enable interrupt 1= masked
　　EINT14 0 = enable interrupt 1= masked
　　EINT13 0 = enable interrupt 1= masked
　　EINT12 0 = enable interrupt 1= masked
　　EINT11 0 = enable interrupt 1= masked
　　EINT10 0 = enable interrupt 1= masked
　　EINT9 0 = enable interrupt 1= masked
　　EINT8 0 = enable interrupt 1= masked
　　EINT7 0 = enable interrupt 1= masked
　　EINT6 0 = enable interrupt 1= masked
　　EINT5 0 = enable interrupt 1= masked
　　EINT4 0 = enable interrupt 1= masked
　　Reserved Reserved
　　但是还有一个疑问，不是说60个中断源吗?除去24个外部中断源应该还有60-24 -(32-6)=10个内部中断源啊。他们在哪呢?
　　其实这里涉及到了子中断源的概念。
　　Sub Sources Descriptions Source
　　INT_AC97 AC97 interrupt INT_WDT_AC97
　　INT_WDT Watchdoc interrupt INT_WDT_AC97
　　INT_CAM_P P-port capture interrupt in camera interface INT_CAM
　　INT_CAM_C C-port capture interrupt in camera interface INT_CAM
　　INT_ADC_S ADC interrupt INT_ADC
　　INT_TC Touch screen interrupt (pen up/down) INT_ADC
　　INT_ERR2 UART2 error interrupt INT_UART2
　　INT_TXD2 UART2 transmit interrupt INT_UART2
　　INT_RXD2 UART2 receive interrupt INT_UART2
　　INT_ERR1 UART1 error interrupt INT_UART1
　　INT_TXD1 UART1 transmit interrupt I NT_UART1
　　INT_RXD1 UART1 receive interrupt INT_UART1
　　INT_ERR0 UART0 error interrupt INT_UART0
　　INT_TXD0 UART0 transmit interrupt INT_UART0
　　INT_RXD0 UART0 receive interrupt NT_UART0