?? pc.c
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/*
*********************************************************************************************************
* PC SUPPORT FUNCTIONS
*
* (c) Copyright 1992-1998, Jean J. Labrosse, Plantation, FL
* All Rights Reserved
*
* File : PC.C
* By : Jean J. Labrosse
*********************************************************************************************************
*/
#include "includes.h"
/*
*********************************************************************************************************
* CONSTANTS
*********************************************************************************************************
*/
#define DISP_BASE 0xB800 /* Base segment of display (0xB800=VGA, 0xB000=Mono) */
#define DISP_MAX_X 80 /* Maximum number of columns */
#define DISP_MAX_Y 25 /* Maximum number of rows */
#define TICK_T0_8254_CWR 0x43 /* 8254 PIT Control Word Register address. */
#define TICK_T0_8254_CTR0 0x40 /* 8254 PIT Timer 0 Register address. */
#define TICK_T0_8254_CTR1 0x41 /* 8254 PIT Timer 1 Register address. */
#define TICK_T0_8254_CTR2 0x42 /* 8254 PIT Timer 2 Register address. */
#define TICK_T0_8254_CTR0_MODE3 0x36 /* 8254 PIT Binary Mode 3 for Counter 0 control word. */
#define TICK_T0_8254_CTR2_MODE0 0xB0 /* 8254 PIT Binary Mode 0 for Counter 2 control word. */
#define TICK_T0_8254_CTR2_LATCH 0x80 /* 8254 PIT Latch command control word */
#define VECT_TICK 0x08 /* Vector number for 82C54 timer tick */
#define VECT_DOS_CHAIN 0x81 /* Vector number used to chain DOS */
/*
*********************************************************************************************************
* LOCAL GLOBAL VARIABLES
*********************************************************************************************************
*/
static INT16U PC_ElapsedOverhead;
static jmp_buf PC_JumpBuf;
static BOOLEAN PC_ExitFlag;
void (*PC_TickISR)(void);
/*$PAGE*/
/*
*********************************************************************************************************
* CLEAR SCREEN
*
* Description : This function clears the PC's screen by directly accessing video RAM instead of using
* the BIOS. It assumed that the video adapter is VGA compatible. Video RAM starts at
* absolute address 0x000B8000. Each character on the screen is composed of two bytes:
* the ASCII character to appear on the screen followed by a video attribute. An attribute
* of 0x07 displays the character in WHITE with a black background.
*
* Arguments : color specifies the foreground/background color combination to use
* (see PC.H for available choices)
*
* Returns : None
*********************************************************************************************************
*/
void PC_DispClrScr (INT8U color)
{
INT8U far *pscr;
INT16U i;
pscr = MK_FP(DISP_BASE, 0x0000);
for (i = 0; i < (DISP_MAX_X * DISP_MAX_Y); i++) { /* PC display has 80 columns and 25 lines */
*pscr++ = ' '; /* Put ' ' character in video RAM */
*pscr++ = color; /* Put video attribute in video RAM */
}
}
/*$PAGE*/
/*
*********************************************************************************************************
* CLEAR A LINE
*
* Description : This function clears one of the 25 lines on the PC's screen by directly accessing video
* RAM instead of using the BIOS. It assumed that the video adapter is VGA compatible.
* Video RAM starts at absolute address 0x000B8000. Each character on the screen is
* composed of two bytes: the ASCII character to appear on the screen followed by a video
* attribute. An attribute of 0x07 displays the character in WHITE with a black background.
*
* Arguments : y corresponds to the desired line to clear. Valid line numbers are from
* 0 to 24. Line 0 corresponds to the topmost line.
*
* color specifies the foreground/background color combination to use
* (see PC.H for available choices)
*
* Returns : None
*********************************************************************************************************
*/
void PC_DispClrLine (INT8U y, INT8U color)
{
INT8U far *pscr;
INT8U i;
pscr = MK_FP(DISP_BASE, (INT16U)y * DISP_MAX_X * 2);
for (i = 0; i < DISP_MAX_X; i++) {
*pscr++ = ' '; /* Put ' ' character in video RAM */
*pscr++ = color; /* Put video attribute in video RAM */
}
}
/*$PAGE*/
/*
*********************************************************************************************************
* DISPLAY A SINGLE CHARACTER AT 'X' & 'Y' COORDINATE
*
* Description : This function writes a single character anywhere on the PC's screen. This function
* writes directly to video RAM instead of using the BIOS for speed reasons. It assumed
* that the video adapter is VGA compatible. Video RAM starts at absolute address
* 0x000B8000. Each character on the screen is composed of two bytes: the ASCII character
* to appear on the screen followed by a video attribute. An attribute of 0x07 displays
* the character in WHITE with a black background.
*
* Arguments : x corresponds to the desired column on the screen. Valid columns numbers are from
* 0 to 79. Column 0 corresponds to the leftmost column.
* y corresponds to the desired row on the screen. Valid row numbers are from 0 to 24.
* Line 0 corresponds to the topmost row.
* c Is the ASCII character to display. You can also specify a character with a
* numeric value higher than 128. In this case, special character based graphics
* will be displayed.
* color specifies the foreground/background color to use (see PC.H for available choices)
* and whether the character will blink or not.
*
* Returns : None
*********************************************************************************************************
*/
void PC_DispChar (INT8U x, INT8U y, INT8U c, INT8U color)
{
INT8U far *pscr;
INT16U offset;
offset = (INT16U)y * DISP_MAX_X * 2 + (INT16U)x * 2; /* Calculate position on the screen */
pscr = MK_FP(DISP_BASE, offset);
*pscr++ = c; /* Put character in video RAM */
*pscr = color; /* Put video attribute in video RAM */
}
/*$PAGE*/
/*
*********************************************************************************************************
* DISPLAY A STRING AT 'X' & 'Y' COORDINATE
*
* Description : This function writes an ASCII string anywhere on the PC's screen. This function writes
* directly to video RAM instead of using the BIOS for speed reasons. It assumed that the
* video adapter is VGA compatible. Video RAM starts at absolute address 0x000B8000. Each
* character on the screen is composed of two bytes: the ASCII character to appear on the
* screen followed by a video attribute. An attribute of 0x07 displays the character in
* WHITE with a black background.
*
* Arguments : x corresponds to the desired column on the screen. Valid columns numbers are from
* 0 to 79. Column 0 corresponds to the leftmost column.
* y corresponds to the desired row on the screen. Valid row numbers are from 0 to 24.
* Line 0 corresponds to the topmost row.
* s Is the ASCII string to display. You can also specify a string containing
* characters with numeric values higher than 128. In this case, special character
* based graphics will be displayed.
* color specifies the foreground/background color to use (see PC.H for available choices)
* and whether the characters will blink or not.
*
* Returns : None
*********************************************************************************************************
*/
void PC_DispStr (INT8U x, INT8U y, INT8U *s, INT8U color)
{
INT8U far *pscr;
INT16U offset;
offset = (INT16U)y * DISP_MAX_X * 2 + (INT16U)x * 2; /* Calculate position of 1st character */
pscr = MK_FP(DISP_BASE, offset);
while (*s) {
*pscr++ = *s++; /* Put character in video RAM */
*pscr++ = color; /* Put video attribute in video RAM */
}
}
/*$PAGE*/
/*
*********************************************************************************************************
* RETURN TO DOS
*
* Description : This functions returns control back to DOS by doing a 'long jump' back to the saved
* location stored in 'PC_JumpBuf'. The saved location was established by the function
* 'PC_DOSSaveReturn()'. After execution of the long jump, execution will resume at the
* line following the 'set jump' back in 'PC_DOSSaveReturn()'. Setting the flag
* 'PC_ExitFlag' to TRUE ensures that the 'if' statement in 'PC_DOSSaveReturn()' executes.
*
* Arguments : None
*
* Returns : None
*********************************************************************************************************
*/
void PC_DOSReturn (void)
{
PC_ExitFlag = TRUE; /* Indicate we are returning to DOS */
longjmp(PC_JumpBuf, 1); /* Jump back to saved environment */
}
/*$PAGE*/
/*
*********************************************************************************************************
* SAVE DOS RETURN LOCATION
*
* Description : This function saves the location of where we are in DOS so that it can be recovered.
* This allows us to abort multitasking under uC/OS-II and return back to DOS as if we had
* never left. When this function is called by 'main()', it sets 'PC_ExitFlag' to FALSE
* so that we don't take the 'if' branch. Instead, the CPU registers are saved in the
* long jump buffer 'PC_JumpBuf' and we simply return to the caller. If a 'long jump' is
* performed using the jump buffer then, execution would resume at the 'if' statement and
* this time, if 'PC_ExitFlag' is set to TRUE then we would execute the 'if' statements and
* restore the DOS environment.
*
* Arguments : None
*
* Returns : None
*********************************************************************************************************
*/
void PC_DOSSaveReturn (void)
{
PC_ExitFlag = FALSE; /* Indicate that we are not exiting yet! */
OSTickDOSCtr = 1; /* Initialize the DOS tick counter */
PC_TickISR = PC_VectGet(VECT_TICK); /* Get MS-DOS's tick vector */
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