cga.c

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/*******************
*Project: 80X86 32BIT MULTI TASKING OPERATING SYSTEM
*Description: driver for MC6845
*
*File: cga.c
*Author: Book Chen
*Date: 2010.01.01
********************
*/
#include "includes.h"

CGA_CONTROL CgaCtrl;

void CgaInit(void){
    CgaCtrl.CursorPosition=0;
    CgaCtrl.CharacterAttribute=0x0f;
    CgaScreenClean();
    OutByte(CGA_ADDRESS_PORT,CGA_CLLR);
    OutByte(CGA_DATA_PORT,((CgaCtrl.CursorPosition/2)&0xff));
    OutByte(CGA_ADDRESS_PORT,CGA_CLHR);
    OutByte(CGA_DATA_PORT,(((CgaCtrl.CursorPosition/2)>>8)&0xff));
}

void CgaCursorSet(void){
    OutByte(CGA_ADDRESS_PORT,CGA_CLLR);
    OutByte(CGA_DATA_PORT,((CgaCtrl.CursorPosition/2)&0xff));
    OutByte(CGA_ADDRESS_PORT,CGA_CLHR);
    OutByte(CGA_DATA_PORT,(((CgaCtrl.CursorPosition/2)>>8)&0xff));
}

void CgaScrollUp(void){
    U32 i;
    U8 ByteValue;
    
    for(i=0;i<3840;i++){
        ByteValue=CgaByteRead(i+160);
        CgaByteWrite(i,ByteValue);
    }
    for(i=3840;i<4000;i=i+2){
        CgaByteWrite(i,' ');
        CgaByteWrite(i+1,CgaCtrl.CharacterAttribute);
    }
    CgaCtrl.CursorPosition=3840;
}

void CgaCharPut(U8 CharValue){
    if((CharValue>=0x20)&&(CharValue<=0x7e)){
         CgaByteWrite(CgaCtrl.CursorPosition++,CharValue);
         CgaByteWrite(CgaCtrl.CursorPosition++,CgaCtrl.CharacterAttribute);
    }
    else{
         CgaByteWrite(CgaCtrl.CursorPosition++,'?');
         CgaByteWrite(CgaCtrl.CursorPosition++,CgaCtrl.CharacterAttribute);
    }
    if(CgaCtrl.CursorPosition==4000) CgaScrollUp();
}

void CgaBackSpace(void){
    if(CgaCtrl.CursorPosition>=2) CgaCtrl.CursorPosition=CgaCtrl.CursorPosition-2;
    CgaByteWrite(CgaCtrl.CursorPosition,' ');
    CgaByteWrite(CgaCtrl.CursorPosition+1,CgaCtrl.CharacterAttribute);
}

void CgaScreenClean(void){
    U32 i;
    
    for(i=0;i<4000;i=i+2){
        CgaByteWrite(i,' ');
        CgaByteWrite(i+1,CgaCtrl.CharacterAttribute);
    }
    CgaCtrl.CursorPosition=0;
}

void CgaChangeLine(void){
    U8 i;
    
    i=0;
    while(CgaCtrl.CursorPosition>160){
        CgaCtrl.CursorPosition=CgaCtrl.CursorPosition-160;
        i++;    
    }
    CgaCtrl.CursorPosition=(i+1)*160;
    if(CgaCtrl.CursorPosition==4000) CgaScrollUp(); 
}

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