Added

Author: wolfram77

01/MAKEFILE

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+#############################################################
+# makefile for TC 2.01 and NASM 0.98                        #
+# The C compiler, NASM and TLINK must be available via the  #
+# PATH variable. Make sure TC_PATH is correct (see below).  #
+#############################################################
+
+TUT_NAME=tut01
+
+TC_PATH=c:\tc
+LIB_PATH=$(TC_PATH)\lib
+
+CC=tcc.exe
+CC_OPTIONS=-1 -k -c -k -ms
+
+ASM=nasm.exe
+ASM_OPTIONS=-f obj
+
+LINK=tlink.exe
+LINK_OPTIONS=/c /x
+
+$(TUT_NAME).exe: $(TUT_NAME).obj pm.obj
+        @$(LINK) $(LINK_OPTIONS) $(LIB_PATH)\c0s $(TUT_NAME) pm, $(TUT_NAME),, $(LIB_PATH)\cs.lib
+
+$(TUT_NAME).obj: $(TUT_NAME).c pm.h
+        @$(CC) $(CC_OPTIONS) $(TUT_NAME).c
+
+pm.obj: pm.asm pm.h
+        @$(ASM) pm.asm $(ASM_OPTIONS)
+
+clean:
+        make
+        del *.obj

01/PM.ASM

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+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; PMode tutorials in C and Asm                          ;;
+;; Copyright (C) 2000 Alexei A. Frounze                  ;;
+;; The programs and sources come under the GPL           ;;
+;; (GNU General Public License), for more information    ;;
+;; read the file gnu-gpl.txt (originally named COPYING). ;;
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+GLOBAL  _read_msw, _read_cr0, _write_cr0
+
+SEGMENT _TEXT PUBLIC CLASS=CODE USE16
+
+_read_msw:
+        smsw    ax
+        retn
+
+_read_cr0:
+        mov     eax, cr0        ; read CR0 to eax
+        mov     edx, eax
+        shr     edx, 16         ; dx:ax = CR0 (return value)
+        retn
+
+_write_cr0:
+        push    bp
+        mov     bp, sp
+        mov     eax, [ss:bp+4]  ; eax = 32-bit parameter
+        mov     cr0, eax
+        pop     bp
+        retn
+
+SEGMENT _DATA PUBLIC CLASS=DATA
+

01/PM.H

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+/*
+  PMode tutorials in C and Asm
+  Copyright (C) 2000 Alexei A. Frounze
+  The programs and sources come under the GPL 
+  (GNU General Public License), for more information
+  read the file gnu-gpl.txt (originally named COPYING).
+*/
+
+#ifndef _pm_h_
+#define _pm_h_
+
+unsigned int    read_msw();
+unsigned long   read_cr0();
+void            write_cr0 (unsigned long value);
+
+#endif

01/TUT01.C

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+/*
+  PMode tutorials in C and Asm
+  Copyright (C) 2000 Alexei A. Frounze
+  The programs and sources come under the GPL 
+  (GNU General Public License), for more information
+  read the file gnu-gpl.txt (originally named COPYING).
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <conio.h>
+#include <dos.h>
+
+#include "pm.h"
+
+#define byte unsigned char
+#define word unsigned int
+
+byte read_CMOS_reg (byte reg) {
+  outportb (0x70, reg);
+  return inportb (0x71);
+}
+
+void write_CMOS_reg (byte reg, byte value) {
+  outportb (0x70, reg);
+  outportb (0x71, value);
+}
+
+void delay_RTC (int secs) {
+  byte x;
+  while (secs--) {
+    x = read_CMOS_reg(0);               /* read seconds from RTC */
+    while (read_CMOS_reg(0) == x);      /* wait for the next value */
+  };
+}
+
+void my_exit() {
+  printf ("\nWe're back...\n");
+  printf ("\nPMode Tutorial by Alexei A. Frounze (c) 2000\n");
+  printf ("E-mail  : [email protected]\n");
+  printf ("Homepage: http://alexfru.chat.ru\n");
+  printf ("Mirror  : http://members.xoom.com/alexfru\n");
+  printf ("PMode...: http://welcome.to/pmode\n");
+}
+
+int main() {
+  unsigned long far *BIOS_timer = MK_FP (0x40, 0x6C);
+
+  clrscr();
+  printf ("Welcome to the 1st PMode tutorial!\n\n");
+  atexit (my_exit);
+
+  if (read_msw() & 1) {
+    printf ("The CPU is already in PMode.\nAborting...");
+    return 0;
+  };
+
+  printf ("We're going to PMode using CR0 for 5 seconds...\n");
+
+  /* disable interrupts so that IRQs don't cause exceptions */
+  disable();
+
+  /* disable NMIs as well */
+  outportb (0x70, inportb(0x70) | 0x80);
+
+  /* WOW!!! This switches us to PMode just setting up CR0.PM bit to 1 */
+  write_cr0 (read_cr0() | 1L);
+
+  /* a delay for 5 seconds */
+  delay_RTC (5);
+
+  /* get out of PMode clearing CR0.PM bit to 0 */
+  write_cr0 (read_cr0() & 0xFFFFFFFEL);
+
+  *BIOS_timer += 91L; /* 5*18.2 ticks total */
+
+  /* enable NMIs */
+  outportb (0x70, inportb(0x70) & 0x7F);
+
+  /* enabling interrupts */
+  enable();
+
+  return 0;
+}