AT91RM9200与S1D13505的LCD调试全过程

AT91RM9200+S1D13505，本来想用S1D13506可惜公司没有库存，大量使用S1D13505，只好慢慢啃了。使用ncs7接S1D13505的片选，使用如下测试程序
  unsigned char * pRegs=0X80000000；
static unsigned short tmp=0x55;
//Step 1: Enable the host interface.
  *(pRegs + 0x1B) = 0x00;              /* 0000 0000 */
  while(1){
  tmp=*((unsigned char *)0x80000000);
  }
一直没有调试通，使用示波器测量结果发现接M/R的A21引脚竟然被拉高，我觉得很奇怪。甚至我去掉pRegs直接硬读0x80000000的版本寄存器内容A21还是被拉高，这是为什么呢？

今天终于解决了S1D13505的LCD显示问题，当初以为两者差不多，偷懒，没有把datasheet从头到尾研究过，最终酿成苦果，花了2天时间才查出问题所在。原来它比S1D13506多了个SUSPEND引脚，用于控制LCD进入省电模式，当MD9下拉时SUSPEND引脚=0时立即进入硬件休眠状态，所有内存与寄存器都不能读写。要读写寄存器必须将SUSPEND引脚拉高。没办法，我飞！飞完后液晶测试正常，可惜没带数码相机。奇怪的是A21引脚依然在我不访问200000地址时还是被周期性拉高，看了一下时许，与CS配合感觉好像是对的。可能是S1D13505内部造成的。

测试程序如下：

/*
**===========================================================================
**Designed for SSC 510T LCD test;
**  The code in this example will perform initialization to the following
**  specification:
**
**  - 640 x 480 dual 16-bit color passive panel.
**  - 75 Hz frame rate.
**  - 8 BPP (256 colors).
**  - 33 MHz input clock.
**  - 2 MB of 60 ns EDO memory.
**---------------------------------------------------------------------------
**  Copyright (c) 2008 WFG
**  All Rights Reserved.
**===========================================================================
*/

/*
** Note that only the upper four bits of the LUT are actually used.
*/
unsigned char LUT8[256*3] =
{
/* Primary and secondary colors */
0x00, 0x00, 0x00,  0x00, 0x00, 0xA0,  0x00, 0xA0, 0x00,  0x00, 0xA0, 0xA0, 
0xA0, 0x00, 0x00,  0xA0, 0x00, 0xA0,  0xA0, 0xA0, 0x00,  0xA0, 0xA0, 0xA0, 
0x50, 0x50, 0x50,  0x00, 0x00, 0xF0,  0x00, 0xF0, 0x00,  0x00, 0xF0, 0xF0, 
0xF0, 0x00, 0x00,  0xF0, 0x00, 0xF0,  0xF0, 0xF0, 0x00,  0xF0, 0xF0, 0xF0, 

/* Gray shades */
0x00, 0x00, 0x00,  0x10, 0x10, 0x10,  0x20, 0x20, 0x20,  0x30, 0x30, 0x30, 
0x40, 0x40, 0x40,  0x50, 0x50, 0x50,  0x60, 0x60, 0x60,  0x70, 0x70, 0x70, 
0x80, 0x80, 0x80,  0x90, 0x90, 0x90,  0xA0, 0xA0, 0xA0,  0xB0, 0xB0, 0xB0, 
0xC0, 0xC0, 0xC0,  0xD0, 0xD0, 0xD0,  0xE0, 0xE0, 0xE0,  0xF0, 0xF0, 0xF0, 

/* Black to red */
0x00, 0x00, 0x00,  0x10, 0x00, 0x00,  0x20, 0x00, 0x00,  0x30, 0x00, 0x00, 
0x40, 0x00, 0x00,  0x50, 0x00, 0x00,  0x60, 0x00, 0x00,  0x70, 0x00, 0x00, 
0x80, 0x00, 0x00,  0x90, 0x00, 0x00,  0xA0, 0x00, 0x00,  0xB0, 0x00, 0x00, 
0xC0, 0x00, 0x00,  0xD0, 0x00, 0x00,  0xE0, 0x00, 0x00,  0xF0, 0x00, 0x00, 

/* Black to green */
0x00, 0x00, 0x00,  0x00, 0x10, 0x00,  0x00, 0x20, 0x00,  0x00, 0x30, 0x00, 
0x00, 0x40, 0x00,  0x00, 0x50, 0x00,  0x00, 0x60, 0x00,  0x00, 0x70, 0x00, 
0x00, 0x80, 0x00,  0x00, 0x90, 0x00,  0x00, 0xA0, 0x00,  0x00, 0xB0, 0x00, 
0x00, 0xC0, 0x00,  0x00, 0xD0, 0x00,  0x00, 0xE0, 0x00,  0x00, 0xF0, 0x00, 

/* Black to blue */
0x00, 0x00, 0x00,  0x00, 0x00, 0x10,  0x00, 0x00, 0x20,  0x00, 0x00, 0x30, 
0x00, 0x00, 0x40,  0x00, 0x00, 0x50,  0x00, 0x00, 0x60,  0x00, 0x00, 0x70, 
0x00, 0x00, 0x80,  0x00, 0x00, 0x90,  0x00, 0x00, 0xA0,  0x00, 0x00, 0xB0, 
0x00, 0x00, 0xC0,  0x00, 0x00, 0xD0,  0x00, 0x00, 0xE0,  0x00, 0x00, 0xF0,

/* Blue to cyan (blue and green) */
0x00, 0x00, 0xF0,  0x00, 0x10, 0xF0,  0x00, 0x20, 0xF0,  0x00, 0x30, 0xF0, 
0x00, 0x40, 0xF0,  0x00, 0x50, 0xF0,  0x00, 0x60, 0xF0,  0x00, 0x70, 0xF0, 
0x00, 0x80, 0xF0,  0x00, 0x90, 0xF0,  0x00, 0xA0, 0xF0,  0x00, 0xB0, 0xF0, 
0x00, 0xC0, 0xF0,  0x00, 0xD0, 0xF0,  0x00, 0xE0, 0xF0,  0x00, 0xF0, 0xF0,

/* Cyan (blue and green) to green */
0x00, 0xF0, 0xF0,  0x00, 0xF0, 0xE0,  0x00, 0xF0, 0xD0,  0x00, 0xF0, 0xC0, 
0x00, 0xF0, 0xB0,  0x00, 0xF0, 0xA0,  0x00, 0xF0, 0x90,  0x00, 0xF0, 0x80, 
0x00, 0xF0, 0x70,  0x00, 0xF0, 0x60,  0x00, 0xF0, 0x50,  0x00, 0xF0, 0x40, 
0x00, 0xF0, 0x30,  0x00, 0xF0, 0x20,  0x00, 0xF0, 0x10,  0x00, 0xF0, 0x00, 

/* Green to yellow (red and green) */
0x00, 0xF0, 0x00,  0x10, 0xF0, 0x00,  0x20, 0xF0, 0x00,  0x30, 0xF0, 0x00, 
0x40, 0xF0, 0x00,  0x50, 0xF0, 0x00,  0x60, 0xF0, 0x00,  0x70, 0xF0, 0x00, 
0x80, 0xF0, 0x00,  0x90, 0xF0, 0x00,  0xA0, 0xF0, 0x00,  0xB0, 0xF0, 0x00, 
0xC0, 0xF0, 0x00,  0xD0, 0xF0, 0x00,  0xE0, 0xF0, 0x00,  0xF0, 0xF0, 0x00, 

/* Yellow (red and green) to red */
0xF0, 0xF0, 0x00,  0xF0, 0xE0, 0x00,  0xF0, 0xD0, 0x00,  0xF0, 0xC0, 0x00, 
0xF0, 0xB0, 0x00,  0xF0, 0xA0, 0x00,  0xF0, 0x90, 0x00,  0xF0, 0x80, 0x00, 
0xF0, 0x70, 0x00,  0xF0, 0x60, 0x00,  0xF0, 0x50, 0x00,  0xF0, 0x40, 0x00, 
0xF0, 0x30, 0x00,  0xF0, 0x20, 0x00,  0xF0, 0x10, 0x00,  0xF0, 0x00, 0x00, 

/* Red to magenta (blue and red) */
0xF0, 0x00, 0x00,  0xF0, 0x00, 0x10,  0xF0, 0x00, 0x20,  0xF0, 0x00, 0x30, 
0xF0, 0x00, 0x40,  0xF0, 0x00, 0x50,  0xF0, 0x00, 0x60,  0xF0, 0x00, 0x70, 
0xF0, 0x00, 0x80,  0xF0, 0x00, 0x90,  0xF0, 0x00, 0xA0,  0xF0, 0x00, 0xB0, 
0xF0, 0x00, 0xC0,  0xF0, 0x00, 0xD0,  0xF0, 0x00, 0xE0,  0xF0, 0x00, 0xF0, 

/* Magenta (blue and red) to blue */
0xF0, 0x00, 0xF0,  0xE0, 0x00, 0xF0,  0xD0, 0x00, 0xF0,  0xC0, 0x00, 0xF0, 
0xB0, 0x00, 0xF0,  0xA0, 0x00, 0xF0,  0x90, 0x00, 0xF0,  0x80, 0x00, 0xF0, 
0x70, 0x00, 0xF0,  0x60, 0x00, 0xF0,  0x50, 0x00, 0xF0,  0x40, 0x00, 0xF0, 
0x30, 0x00, 0xF0,  0x20, 0x00, 0xF0,  0x10, 0x00, 0xF0,  0x00, 0x00, 0xF0,

/* Black to magenta (blue and red) */
0x00, 0x00, 0x00,  0x10, 0x00, 0x10,  0x20, 0x00, 0x20,  0x30, 0x00, 0x30, 
0x40, 0x00, 0x40,  0x50, 0x00, 0x50,  0x60, 0x00, 0x60,  0x70, 0x00, 0x70, 
0x80, 0x00, 0x80,  0x90, 0x00, 0x90,  0xA0, 0x00, 0xA0,  0xB0, 0x00, 0xB0, 
0xC0, 0x00, 0xC0,  0xD0, 0x00, 0xD0,  0xE0, 0x00, 0xE0,  0xF0, 0x00, 0xF0, 

/* Black to cyan (blue and green) */
0x00, 0x00, 0x00,  0x00, 0x10, 0x10,  0x00, 0x20, 0x20,  0x00, 0x30, 0x30, 
0x00, 0x40, 0x40,  0x00, 0x50, 0x50,  0x00, 0x60, 0x60,  0x00, 0x70, 0x70, 
0x00, 0x80, 0x80,  0x00, 0x90, 0x90,  0x00, 0xA0, 0xA0,  0x00, 0xB0, 0xB0, 
0x00, 0xC0, 0xC0,  0x00, 0xD0, 0xD0,  0x00, 0xE0, 0xE0,  0x00, 0xF0, 0xF0, 

/* Red to white */
0xF0, 0x00, 0x00,  0xF0, 0x10, 0x10,  0xF0, 0x20, 0x20,  0xF0, 0x30, 0x30, 
0xF0, 0x40, 0x40,  0xF0, 0x50, 0x50,  0xF0, 0x60, 0x60,  0xF0, 0x70, 0x70, 
0xF0, 0x80, 0x80,  0xF0, 0x90, 0x90,  0xF0, 0xA0, 0xA0,  0xF0, 0xB0, 0xB0, 
0xF0, 0xC0, 0xC0,  0xF0, 0xD0, 0xD0,  0xF0, 0xE0, 0xE0,  0xF0, 0xF0, 0xF0, 

/* Green to white */
0x00, 0xF0, 0x00,  0x10, 0xF0, 0x10,  0x20, 0xF0, 0x20,  0x30, 0xF0, 0x30, 
0x40, 0xF0, 0x40,  0x50, 0xF0, 0x50,  0x60, 0xF0, 0x60,  0x70, 0xF0, 0x70, 
0x80, 0xF0, 0x80,  0x90, 0xF0, 0x90,  0xA0, 0xF0, 0xA0,  0xB0, 0xF0, 0xB0, 
0xC0, 0xF0, 0xC0,  0xD0, 0xF0, 0xD0,  0xE0, 0xF0, 0xE0,  0xF0, 0xF0, 0xF0, 

/* Blue to white */
0x00, 0x00, 0xF0,  0x10, 0x10, 0xF0,  0x20, 0x20, 0xF0,  0x30, 0x30, 0xF0, 
0x40, 0x40, 0xF0,  0x50, 0x50, 0xF0,  0x60, 0x60, 0xF0,  0x70, 0x70, 0xF0, 
0x80, 0x80, 0xF0,  0x90, 0x90, 0xF0,  0xA0, 0xA0, 0xF0,  0xB0, 0xB0, 0xF0, 
0xC0, 0xC0, 0xF0,  0xD0, 0xD0, 0xF0,  0xE0, 0xE0, 0xF0,  0xF0, 0xF0, 0xF0
};
                 

/*
** REGISTER_OFFSET points to the starting address of the S1D13505 registers
*/
#define REGISTER_OFFSET    ((unsigned char *) 0x80000000)

/*
** DISP_MEM_OFFSET points to the starting address of the display buffer memory
*/
#define DISP_MEM_OFFSET  ((unsigned char *) 0x80200000)

/*
** DISP_MEMORY_SIZE is the size of display buffer memory
*/
#define DISP_MEMORY_SIZE   0x200000

/*
** Calculate the value to put in Ink/Cursor Start Address Select Register
**   Offset = (DISP_MEM_SIZE - (X * 8192)
** We want the offset to be just past the end of display memory so:
**   (640 * 480) = DISP_MEMORY_SIZE - (X * 8192)
**
**   CURSOR_START = (DISP_MEMORY_SIZE - (640 * 480)) / 8192
*/
#define CURSOR_START   218

void LCD_Test(void)
{
  unsigned char * pRegs = REGISTER_OFFSET;
  unsigned char * pMem;
  unsigned char * pLUT;
  unsigned char * pTmp;
  unsigned char * pCursor;
  static unsigned short tmp=0x55;
  long lpCnt;
  int idx;
  int rgb;
  long x, y;

  /*
  ** Initialize the chip.
  */

  /*
  ** Step 1: Enable the host interface.
  **
  ** Register 1B: Miscellaneous Disable - host interface enabled, half frame
  **              buffer enabled.
  */
  *(pRegs + 0x1B) = 0x00;              /* 0000 0000 */

  //add by wfg
//  while(1){
  tmp=*((volatile unsigned char *)0x80000000);
 // *((unsigned char *)0x8020001b) = 0x00;
 // }
  /*
  ** Step 2: Disable the FIFO
  */
  *(pRegs + 0x23) = 0x80;              /* 1000 0000 */

  /*
  ** Step 3: Set Memory Configuration
  **
  ** Register 1: Memory Configuration - 5 ms refresh, EDO
  */
  *(pRegs + 0x01) = 0x40;              /* 0011 0000 */

  /*
  ** Step 4: Set Performance Enhancement 0 register
  */
  *(pRegs + 0x22) = 0x24;              /* 0010 0100 */

  /*
  ** Step 5: Set the rest of the registers in order.
  */

  /*
  ** Register 2: Panel Type - 16-bit, format 1, color, dual, passive.
  */
  *(pRegs + 0x02) = 0x26;              /* 0010 0110 */

  /*
  ** Register 3: Mod Rate
  */
  *(pRegs + 0x03) = 0x00;              /* 0000 0000 */

  /*
  ** Register 4: Horizontal Display Width (HDP) - 640 pixels
  **             (640 / 8) - 1 = 79t = 4Fh
  */
  *(pRegs + 0x04) = 0x4f;              /* 0100 1111 */

  /*
  ** Register 5: Horizontal Non-Display Period (HNDP)
  **                                      PCLK
  **             Frame Rate = -----------------------------
  **                           (HDP + HNDP) * (VDP + VNDP)
  **
  **                                   16,500,000
  **                        = -----------------------------
  **                           (640 + HNDP) * (480 + VNDP)
  **
  ** HNDP and VNDP must be calculated such that the desired frame rate
  ** is achieved.
  */
  *(pRegs + 0x05) = 0x1F;              /* 0001 1111 */

  /*
  ** Register 6: HRTC/FPLINE Start Position - applicable to CRT/TFT only.
  */
  *(pRegs + 0x06) = 0x00;              /* 0000 0000 */

  /*
  ** Register 7: HRTC/FPLINE Pulse Width - applicable to CRT/TFT only.
  */
  *(pRegs + 0x07) = 0x00;              /* 0000 0000 */

  /*
  ** Registers 8-9: Vertical Display Height (VDP) - 480 lines.
  **                480/2 - 1 = 239t = 0xEF
  */
  *(pRegs + 0x08) = 0xEF;              /* 1110 1111 */
  *(pRegs + 0x09) = 0x00;              /* 0000 0000 */

  /*
  ** Register A: Vertical Non-Display Period (VNDP)
  **             This register must be programed with register 5 (HNDP)
  **             to arrive at the frame rate closest to the desired
  **             frame rate.
  */
  *(pRegs + 0x0A) = 0x01;              /* 0000 0001 */

  /*
  ** Register B: VRTC/FPFRAME Start Position - applicable to CRT/TFT only.
  */
  *(pRegs + 0x0B) = 0x00;              /* 0000 0000 */

  /*
  ** Register C: VRTC/FPFRAME Pulse Width - applicable to CRT/TFT only.
  */
  *(pRegs + 0x0C) = 0x00;              /* 0000 0000 */

  /*
  ** Register D: Display Mode - 8 BPP, LCD disabled.
  */
  *(pRegs + 0x0D) = 0x0C;              /* 0000 1100 */

  /*
  ** Registers E-F: Screen 1 Line Compare - unless setting up for
  **                split screen operation use 0x3FF.
  */
  *(pRegs + 0x0E) = 0xFF;              /* 1111 1111 */
  *(pRegs + 0x0F) = 0x03;              /* 0000 0011 */

  /*
  ** Registers 10-12: Screen 1 Display Start Address - start at the
  **                  first byte in display memory.
  */
  *(pRegs + 0x10) = 0x00;              /* 0000 0000 */
  *(pRegs + 0x11) = 0x00;              /* 0000 0000 */
  *(pRegs + 0x12) = 0x00;              /* 0000 0000 */

  /*
  ** Register 13-15: Screen 2 Display Start Address - not applicable
  **                 unless setting up for split screen operation.
  */
  *(pRegs + 0x13) = 0x00;              /* 0000 0000 */
  *(pRegs + 0x14) = 0x00;              /* 0000 0000 */
  *(pRegs + 0x15) = 0x00;              /* 0000 0000 */

  /*
  ** Register 16-17: Memory Address Offset - this address represents the
  **                 starting WORD. At 8BPP our 640 pixel width is 320
  **                 WORDS
  */
  *(pRegs + 0x16) = 0x40;              /* 0100 0000 */
  *(pRegs + 0x17) = 0x01;              /* 0000 0001 */

  /*
  ** Register 18: Pixel Panning
  */
  *(pRegs + 0x18) = 0x00;              /* 0000 0000 */

  /*
  ** Register 19: Clock Configuration - In this case we must divide
  **              PCLK by 2 to arrive at the best frequency to set
  **              our desired panel frame rate.
  */
  *(pRegs + 0x19) = 0x01;              /* 0000 0001 */

  /*
  ** Register 1A: Power Save Configuration - enable LCD power, CBR refresh,
  **              not suspended.
  */
  *(pRegs + 0x1A) = 0x00;              /* 0000 0000 */

  /*
  ** Register 1C-1D: MD Configuration Readback - these registers are
  **                 read only, but it's OK to write a 0 to keep
  **                 the register configuration logic simpler.
  */
  *(pRegs + 0x1C) = 0x00;              /* 0000 0000 */
  *(pRegs + 0x1D) = 0x00;              /* 0000 0000 */

  /*
  ** Register 1E-1F: General I/O Pins Configuration
  */
  *(pRegs + 0x1E) = 0x00;              /* 0000 0000 */
  *(pRegs + 0x1F) = 0x00;              /* 0000 0000 */

  /*
  ** Register 20-21: General I/O Pins Control
  */
  *(pRegs + 0x20) = 0x00;              /* 0000 0000 */
  *(pRegs + 0x21) = 0x00;              /* 0000 0000 */

  /*
  ** Registers 24-26: LUT control.
  **                  For this example do a typical 8 BPP LUT setup.
  **
  ** Setup the pointer to the LUT data and reset the LUT index register.
  ** Then, loop writing each of the RGB LUT data elements.
  */
  pLUT = LUT8;
  *(pRegs + 0x24) = 0;

  for (idx = 0; idx < 256; idx++)
  {
    for (rgb = 0; rgb < 3; rgb++)
    {
      *(pRegs + 0x26) = *pLUT;
      pLUT++;
    }
  }

  /*
  ** Register 27: Ink/Cursor Control - disable ink/cursor
  */
  *(pRegs + 0x27) = 0x00;              /* 0000 0000 */

  /*
  ** Registers 28-29: Cursor X Position
  */
  *(pRegs + 0x28) = 0x00;              /* 0000 0000 */
  *(pRegs + 0x29) = 0x00;              /* 0000 0000 */

  /*
  ** Registers 2A-2B: Cursor Y Position
  */
  *(pRegs + 0x2A) = 0x00;              /* 0000 0000 */
  *(pRegs + 0x2B) = 0x00;              /* 0000 0000 */

  /*
  ** Registers 2C-2D: Ink/Cursor Color 0 - blue
  */
  *(pRegs + 0x2C) = 0x1F;              /* 0001 1111 */
  *(pRegs + 0x2D) = 0x00;              /* 0000 0000 */

  /*
  ** Registers 2E-2F: Ink/Cursor Color 1 - green
  */
  *(pRegs + 0x2E) = 0xE0;              /* 1110 0000 */
  *(pRegs + 0x2F) = 0x07;              /* 0000 0111 */

  /*
  ** Register 30: Ink/Cursor Start Address Select
  */
  *(pRegs + 0x30) = 0x00;              /* 0000 0000 */

  /*
  ** Register 31: Alternate FRM Register
  */
  *(pRegs + 0x31) = 0x00;

  /*
  ** Register 23: Performance Enhancement - display FIFO enabled, optimum
  **              performance. The FIFO threshold is set to 0x00; for
  **              15/16 bpp modes, set the FIFO threshold
  **              to a higher value, such as 0x1B.
  */
  *(pRegs + 0x23) = 0x00;              /* 0000 0000 */

  /*
  ** Register D: Display Mode - 8 BPP, LCD enable.
  */
  *(pRegs + 0x0D) = 0x0D;              /* 0000 1101 */

 

  /*
  ** Clear memory by filling 2 MB with 0
  */
  pMem = DISP_MEM_OFFSET;

  for (lpCnt = 0; lpCnt < DISP_MEMORY_SIZE; lpCnt++)
  {
    *pMem = 0;
    pMem++;
  }

  /*
  ** Draw a 100x100 red rectangle in the upper left corner (0, 0)
  ** of the display.
  */
  pMem = DISP_MEM_OFFSET;

  for (y = 0; y < 100; y++)
  {
    pTmp = pMem + y * 640L;

    for (x = 0; x < 100; x++)
    {
      *pTmp = 0x0c;
      pTmp++;
    }
  }

  /*
  ** Init the HW cursor. In this example the cursor memory will be located
  ** immediately after display memory. Why here? Because it's an easy
  ** location to calculate and will not interfere with the half frame buffer.
  ** Additionally, the HW cursor can be turned into an ink layer quite
  ** easily from this location.
  */
  *(pRegs + 0x30) = CURSOR_START;

  pTmp = pCursor = pMem + (DISP_MEMORY_SIZE - (CURSOR_START * 8192L));

  /*
  ** Set the contents of the cursor memory such that the cursor
  ** is transparent. To do so, write a 10101010b pattern in each byte.
  ** The cursor is 2 bpp so a 64x64 cursor requires
  ** 64/4 * 64 = 1024 bytes of memory.
  */
  for (lpCnt = 0; lpCnt < 1024; lpCnt++)
    {
    *pTmp = 0xAA;
    pTmp++;
    }

  /*
  ** Set the first user definable cursor color to black and
  ** the second user definable cursor color to white.
  */
  *(pRegs + 0x2C) = 0;
  *(pRegs + 0x2D) = 0;
  *(pRegs + 0x2E) = 0xFF;
  *(pRegs + 0x2F) = 0xFF;

  /*
  ** Draw a hollow rectangle around the cursor.
  */
  pTmp = pCursor;

  for (lpCnt = 0; lpCnt < 16; lpCnt++)
  {
    *pTmp = 0x55;
    pTmp++;
  }

  for (lpCnt = 0; lpCnt < 14; lpCnt++)
  {
    *pTmp = 0x6A;
    pTmp += 15;

    *pTmp = 0xA9;
    pTmp++;
  }

  for (lpCnt = 0; lpCnt < 16; lpCnt++)
  {
    *pTmp = 0x55;
    pTmp++;
  }

  /*
  ** Move the cursor to 100, 100.
  */

  /*
  ** First we wait for the next vertical non-display
  ** period before updating the position registers.
  */
  while (*(pRegs + 0x0A) & 0x80);     /* wait while in VNDP */

  while (!(*(pRegs + 0x0A) & 0x80));  /* wait while in VDP */

  /*
  ** Now update the position registers.
  */
  *(pRegs + 0x28) = 100;   /* Set Cursor X = 100 */
  *(pRegs + 0x29) = 0x00;

  *(pRegs + 0x2A) = 100;   /* Set Cursor Y = 100 */
  *(pRegs + 0x2B) = 0x00;

  /*
  ** Enable the hardware cursor.
  */
  *(pRegs + 0x27) = 0x40;
}

 此段程序成功让液晶在红绿蓝间切换。可是还不能实现方框的绘制的功能，奇怪，为什么呢？