this is a code for scaling down for css. i was wondering, how this worked. please someone explain to me part by part. thank you very much.

/* ======================================================================== / / Copyright (C) 2000 - 2009 ND-Tech. Co., Ltd. / / All Rights Reserved. / / ======================================================================== / / Project : ScaleDown Created : 31-AUG-2009 / / File : main.c Contact : [email protected] / / ======================================================================== / / You are free to use or modify this code to the following restrictions: / / Acknowledge ND Tech. Co. Ltd. / / Or, put "Parts of code by ND Tech. Co., Ltd." / / Or, leave this header as it is. / / in somewhere in your code. / / ======================================================================== */

include "vm3224k.h"

define CE0CTL *(volatile int *)(0x01800008)

define CE2CTL *(volatile int *)(0x01800010)

define SDCTL *(volatile int *)(0x01800018)

define LED *(volatile short *)(0x90080000)

// Definitions for async access(change as you wish)

define WSU (2<<28) // Write Setup : 0-15

define WST (8<<22) // Write Strobe: 0-63

define WHD (2<<20) // Write Hold : 0-3

define RSU (2<<16) // Read Setup : 0-15

define TA (3<<14) // Turn Around : 0-3

define RST (8<<8) // Read Strobe : 0-63

define RHD (2<<0) // Read Hold : 0-3

define MTYPE (2<<4)

/* EDMA Registers */

define PaRAM_OPT 0 // Options

define PaRAM_SRC 1 // Source Address

define PaRAM_CNT 2 // Frame count, Element count

define PaRAM_DST 3 // Destination Address

define PaRAM_IDX 4 // Frame index, Element index

define PaRAM_RDL 5 // Element count reload, Link address

define EDMA_CIPR *(volatile int *)0x01A0FFE4 // EDMA Channel interrupt pending low register

define EDMA_CIER *(volatile int *)0x01A0FFE8 // EDMA Channel interrupt enable low register

define EDMA_CCER *(volatile int *)0x01A0FFEC // EDMA Channel chain enable register

define EDMA_ER *(volatile int *)0x01A0FFF0 // EDMA Event low register

define EDMA_EER *(volatile int *)0x01A0FFF4 // EDMA Event enable low register

define EDMA_ECR *(volatile int *)0x01A0FFF8 // EDMA Event clear low register

define EDMA_ESR *(volatile int *)0x01A0FFFC // EDMA Event set low register

define PRI (2<<29) // 1:High priority, 2:Low priority

define ESIZE (1<<27) // 0:32bit, 1:16bit, 2:8bit, 3:reserved

define DS2 (0<<26) // 1:2-Dimensional

define SUM (0<<24) // 0:no update, 1:increment, 2:decrement, 3:by index

define DD2 (0<<23) // 1:2-Dimensional

define DUM (0<<21) // 0:no update, 1:increment, 2:decrement, 3:by index

define TCINT (1<<20) // 0:disable, 1:enable

define TCC (8<<16) // 4 bit code

define LINK (0<<1) // 0:disable, 1:enable

define FS (1<<0) // 0:element, 1:frame

define OptionField_0 (PRI|ESIZE|DS2|SUM|DD2|DUM|TCINT|TCC|LINK|FS)

define DD2_1 (1<<23) // 1:2-Dimensional

define DUM_1 (1<<21) // 0:no update, 1:increment, 2:decrement, 3:by index

define TCC_1 (9<<16) // 4 bit code

define OptionField_1 (PRI|ESIZE|DS2|SUM|DD2_1|DUM_1|TCINT|TCC_1|LINK|FS)

define TCC_2 (10<<16)// 4 bit code

define OptionField_2 (PRI|ESIZE|DS2|SUM|DD2|DUM|TCINT|TCC_2|LINK|FS)

define DS2_3 (1<<26) // 1:2-Dimensional

define SUM_3 (1<<24) // 0:no update, 1:increment, 2:decrement, 3:by index

define TCC_3 (11<<16)// 4 bit code

define OptionField_3 (PRI|ESIZE|DS2_3|SUM_3|DD2|DUM|TCINT|TCC_3|LINK|FS)

pragma DATA_SECTION ( lcd,".sdram" )

pragma DATA_SECTION ( cam,".sdram" )

pragma DATA_SECTION ( rgb,".sdram" )

pragma DATA_SECTION ( u,".sdram" )

extern cregister volatile unsigned int IER; extern cregister volatile unsigned int CSR;

short camcode = 0x08000; short lcdcode = 0x00000; short lcd[2][240][320]; short cam[2][240][320]; short rgb[64][32][32]; short bufsel; int *Cevent,*Levent,*CLink,flag=1; unsigned char v[240][160],out_y[120][160]; unsigned char y[240][320],out_u[120][80]; unsigned char u[240][160],out_v[120][80];

void PLL6713() { int i; // CPU Clock Input : 50MHz

            *(volatile int *)(0x01b7c100) = *(volatile int *)(0x01b7c100) & 0xfffffffe;
            for(i=0;i<4;i++);
            *(volatile int *)(0x01b7c100) = *(volatile int *)(0x01b7c100) | 0x08;
            *(volatile int *)(0x01b7c114) = 0x08001;  // 50MHz/2 = 25MHz
            *(volatile int *)(0x01b7c110) = 0x0c;     // 25MHz * 12 = 300MHz
            *(volatile int *)(0x01b7c118) = 0x08000;  // SYSCLK1 = 300MHz/1 = 300MHz
            *(volatile int *)(0x01b7c11c) = 0x08001;  // SYSCLK2 = 300MHz/2 = 150MHz // Peripheral Clock
            *(volatile int *)(0x01b7c120) = 0x08003;  // SYSCLK3 = 300MHz/4 =  75MHz // SDRAM Clock
            for(i=0;i<4;i++);
            *(volatile int *)(0x01b7c100) = *(volatile int *)(0x01b7c100) & 0xfffffff7;
            for(i=0;i<4;i++);
            *(volatile int *)(0x01b7c100) = *(volatile int *)(0x01b7c100) | 0x01;

}

unsigned short ybr_565(short y,short u,short v) { int r,g,b;

            b = y + 1772*(u-128)/1000;
            if (b<0) b=0;
            if (b>255) b=255;
            g = y - (344*(u-128) + 714*(v-128))/1000;
            if (g<0) g=0;
            if (g>255) g=255;
            r = y + 1402*(v-128)/1000;
            if (r<0) r=0;
            if (r>255) r=255;
            return ((r&0x0f8)<<8)|((g&0x0fc)<<3)|((b&0x0f8)>>3);

}

void yuyv2yuv(char *yuyv,char *y,char *u,char *v) { int i,j,dy,dy1,dy2,s;

            for (j=s=dy=dy1=dy2=0;j<240;j++) {
                            for (i=0;i<320;i+=2) {
                                            u[dy1++] = yuyv[s++];
                                            y[dy++]  = yuyv[s++];
                                            v[dy2++] = yuyv[s++];
                                            y[dy++]  = yuyv[s++];
                            }
            }

}

interrupt void c_int06(void) { if(EDMA_CIPR&0x800){ EDMA_CIPR = 0xffff; bufsel=(++bufsel&0x01); Cevent[PaRAM_DST] = (int)cam[(bufsel+1)&0x01]; Levent[PaRAM_SRC] = (int)lcd[(bufsel+1)&0x01];
EDMA_ESR = 0x80; flag=1; } }

void main() { int i,j,k,y0,y1,v0,u0; bufsel = 0; CSR &= (~0x1); PLL6713(); // Initialize C6713 PLL
CE0CTL = 0xffffbf33;// SDRAM Space CE2CTL = (WSU|WST|WHD|RSU|RST|RHD|MTYPE); SDCTL = 0x57115000; vm3224init(); // Initialize vm3224k2 vm3224rate(1); // Set frame rate vm3224bl(15); // Set backlight VM3224CNTL = VM3224CNTL&0xffff | 0x2; // vm3224 interrupt enable

            for (k=0;k<64;k++)  // Create RGB565 lookup table
for (i=0;i<32;i++)
for (j=0;j<32;j++) rgb[k][i][j] = ybr_565(k<<2,i<<3,j<<3);

            Cevent                                   = (int *)(0x01a00000 + 24 * 7);
            Cevent[PaRAM_OPT] = OptionField_0;                                                                
            Cevent[PaRAM_SRC] = (int)&camcode;                               
            Cevent[PaRAM_CNT] = 1;
            Cevent[PaRAM_DST] = (int)&VM3224ADDH;

            Cevent                                 = (int *)(0x01a00000 + 24 * 8);
            Cevent[PaRAM_OPT] = OptionField_1;                                                                
            Cevent[PaRAM_SRC] = (int)&VM3224DATA;
            Cevent[PaRAM_CNT] = (239<<16)|320;
            Cevent[PaRAM_DST] = (int)cam[bufsel];             
            Cevent[PaRAM_IDX] = 0;

            Levent                                   = (int *)(0x01a00000 + 24 * 9);
            Levent[PaRAM_OPT] = OptionField_2;                                                                 
            Levent[PaRAM_SRC] = (int)&lcdcode;                                   
            Levent[PaRAM_CNT] = 1;
            Levent[PaRAM_DST] = (int)&VM3224ADDH;

            Levent                                   = (int *)(0x01a00000 + 24 * 10);
            Levent[PaRAM_OPT] = OptionField_3;                                                                 
            Levent[PaRAM_SRC] = (int)lcd[bufsel];                                
            Levent[PaRAM_CNT] = (239<<16)|320;
            Levent[PaRAM_DST] = (int)&VM3224DATA;
            Levent[PaRAM_IDX] = 0;             

            IER = IER | (1<<6)|3;
            CSR = CSR | 0x1;

            EDMA_CCER = (1<<8)|(1<<9)|(1<<10);
            EDMA_CIER = (1<<11);
            EDMA_CIPR = 0xffff;
            EDMA_ESR = 0x80;

            while (1) {
                            if(flag) {

// LED = 0; yuyv2yuv((char *)cam[bufsel],(char *)y,(char *)u,(char *)v);

                                            for(j=0;j<240;j++)
                                            for(i=0;i<320;i++) lcd[bufsel][j][i]=0;
                                            for(j=0;j<240;j+=2)
                                            for(i=0;i<320;i+=2)
                                                            out_y[j>>1][i>>1]=(y[j][i]+y[j][i+1]+y[j+1][i]+y[j+1][i+1])>>2;
                                            for(j=0;j<240;j+=2)
                                            for(i=0;i<160;i+=2) {
                                                            out_u[j>>1][i>>1]=(u[j][i]+u[j][i+1]+u[j+1][i]+u[j+1][i+1])>>2;
                                                            out_v[j>>1][i>>1]=(v[j][i]+v[j][i+1]+v[j+1][i]+v[j+1][i+1])>>2;
                                            }
                                            for (j=0;j<120;j++)
                                            for (i=0;i<160;i+=2) {
                                                            y0 = out_y[j][i]>>2;
                                                            u0 = out_u[j][i>>1]>>3;                                               
                                                            v0 = out_v[j][i>>1]>>3;                                                
                                                            y1 = out_y[j][i+1]>>2;                                   
                                                            lcd[bufsel][j+60][i+80]=rgb[y0][u0][v0];
                                                            lcd[bufsel][j+60][i+81]=rgb[y1][u0][v0];
                                            }
                                            flag=0;

// LED = 1; } } }