注：对于一个已知尺寸的LCD屏，只要确定了VCLK值，行频和场频就应该知道了。但这样还不行的，因为在每一帧时钟信号中，还会有一些与屏显示无关的时钟出现，这就给确定行频和场频带来了一定的复杂性。如在HSYNC信号先后会有水平同步信号前肩（HFPD）和水平同步信号后肩（HBPD）出现，在VSYNC信号先后会有垂直同步信号前肩（VFPD）和垂直同步信号后肩（VBPD）出现，在这些信号时序内，不会有有效像素信号出现，另外HSYNC和VSYNC信号有效时，其电平要保持一定的时间，它们分别叫做水平同步信号脉宽HSPW和垂直同步信号脉宽VSPW，这段时间也不能有像素信号。因此计算行频和场频时，一定要包括这些信号。
对于以上这些参数的值将分别保存到REGBANK寄存器组中的LCDCON1/2/3/4/5寄存器中：(对寄存器的操作请查看S3c2440数据手册LCD部分)
4. 帧缓冲(FrameBuffer)：
帧缓冲是Linux为显示设备提供的一个接口，它把一些显示设备描述成一个缓冲区，允许应用程序通过 FrameBuffer定义好的接口访问这些图形设备，从而不用去关心具体的硬件细节。对于帧缓冲设备而言，只要在显示缓冲区与显示点对应的区域写入颜色 值，对应的颜色就会自动的在屏幕上显示。下面来看一下在不同色位模式下缓冲区与显示点的对应关系：
volatile static unsigned short LCD_BUFFER[240][320];
void Pixel(U32 x,U32 y, U16 c )
{
if ( (x < SCR_XSIZE_TFT_320240) && (y < SCR_YSIZE_TFT_320240) )
LCD_BUFFER[y][x] = c;
}
很容易发现TFT LCD上显示单个像素的函数实际上很简洁,看来似乎只需要LCD_BUFFER[(y)][(x)] = c这一句话.下面就来分析下，是如何通过这一句话来实现在LCD上显示单个像素的,先分析下Lcd_Init()即LCD初始化函数：
#define rGPCCON(*(volatile unsigned *)0x56000020)
#define rGPCUP(*(volatile unsigned *)0x56000028)
#define rGPDCON(*(volatile unsigned *)0x56000030)
#define rGPDUP(*(volatile unsigned *)0x56000038)
#define rLCDCON1(*(volatile unsigned *)0x4d000000)
#define rLCDCON2(*(volatile unsigned *)0x4d000004)
#define rLCDCON3(*(volatile unsigned *)0x4d000008)
#define rLCDCON4(*(volatile unsigned *)0x4d00000c)
#define rLCDCON5(*(volatile unsigned *)0x4d000010)
#define rLCDSADDR1(*(volatile unsigned *)0x4d000014)
#define rLCDSADDR2(*(volatile unsigned *)0x4d000018)
#define rLCDSADDR3(*(volatile unsigned *)0x4d00001c)
#define rLCDINTMSK(*(volatile unsigned *)0x4d00005c)
#define rTPAL(*(volatile unsigned *)0x4d000050)
void Lcd_Init(void)
{
rGPCUP=0xffffffff;// Disable Pull-up register
rGPCCON=0xaaaa56a9; //Initialize VD[7:0],LCDVF[2:0],VM,VFRAME,VLINE,VCLK,LEND
rGPDUP=0xffffffff;// Disable Pull-up register
rGPDCON=0xaaaaaaaa; //Initialize VD[15:8]
//LCDCON1: TFT LCD panel,MMODE[7]=0,16bpp TFT,ENVID=off
rLCDCON1=(CLKVAL_TFT_320240<8)|(MVAL_USED<7)|(3<5)|(12<1)|0;
rLCDCON2=(VBPD_320240<24)|(LINEVAL_TFT_320240<14)|(VFPD_320240<6)|(VSPW_320240);
rLCDCON3=(HBPD_320240<19)|(HOZVAL_TFT_320240<8)|(HFPD_320240);
rLCDCON4=(MVAL<8)|(HSPW_320240);
rLCDCON5=(1<11)|(1<9)|(1<8)|(1<3)|(BSWP<1)|(HWSWP);
//rLCDCON5=(1<11)|(0<9)|(0<8)|(0<6)|(BSWP<1)|(HWSWP);
//FRM5:6:5,HSYNC and VSYNC are inverted
//LCDBANK[29:21] = (U32)LCD_BUFFER >> 22 : These bits indicate A[30:22] of the bank location for the video buffer in the system memory. LCDBANK value cannot be changed even when moving the view port. LCD frame buffer should be within aligned 4MB region, which ensures that LCDBANK value will not be changed when moving the view port. So, care should be taken to use the malloc() function.
//系统内存地址A[30:22]处的Bank位置为图像缓冲。LCDBANK的值在视图移动的值在视图移动时不能改变，LCD帧缓冲应该在4MB区域对齐，保证LCDBANK的值在移动视图时不会改变。
//LCDBASEU[20:0] = ((U32)LCD_BUFFER >> 1)&0x1fffff : For dual-scan LCD : These bits indicate A[21:1] of the start address of the upper address counter, which is for the upper frame memory of dual scan LCD or the frame memory of single scan LCD.
//For single-scan LCD : These bits indicate A[21:1] of the start address of the LCD frame buffer.
//双扫描：表明高地址计数器的起始地址A[21:1]，用于LCD双扫描的上部帧内存或者单扫描的帧内存
//单扫描：表明LCD帧缓冲的起始地址A[21:1]
rLCDSADDR1=(((U32)LCD_BUFFER>>22)<21)|M5D((U32)LCD_BUFFER>>1);
//LCDSADDR2 0x4d000018帧缓冲起始寄存器2:
//LCDBASEL[20:0] = ((LCD_ADDR + LCD_WIDTH * LCD_HEIGHT * 2) >> 1)& 0x1fffff = (LCD_ADDR >> 1 + LCD_WIDTH * LCD_HEIGHT)& 0x1fffff
//For dual-scan LCD: These bits indicate A[21:1] of the start address of the lower address counter, which is used for the lower frame memory of dual scan LCD.
//For single scan LCD: These bits indicate A[21:1] of the end address of the LCD frame buffer.
//LCDBASEL = ((the frame end address) >>1) + 1 = LCDBASEU + (PAGEWIDTH+OFFSIZE) x (LINEVAL+1)
//双扫描：表明低地址计数器的起始地址A[21:1]，用于LCD双扫描的下部帧内存或者单扫描的帧内存
//单扫描：表明LCD帧缓冲的结束地址A[21:1]
rLCDSADDR2=M5D( ((U32)LCD_BUFFER+(SCR_XSIZE_TFT_320240*LCD_YSIZE_TFT_320240*2))>>1 );
//LCDSADDR3 0x4d00001c帧缓冲起始寄存器3:
//OFFSIZE = 0;PAGEWIDTH = 320 虚拟屏页宽（半字数量）定义了帧中的视图域宽度
rLCDSADDR3=(((SCR_XSIZE_TFT_320240-LCD_XSIZE_TFT_320240)/1)<11)|(LCD_XSIZE_TFT_320240/1);
rLCDINTMSK|=(3);// MASK LCD Sub Interrupt
//rTCONSEL|=((1<4)|1); // Disable LCC3600, LPC3600
rTPAL=0;// Disable Temp Palette
}
