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Lecture # 19
Reading the Date
#include <bios.h> #include <dos.h> void main () { unsigned int cen,yrs,mons,days; _AH =4; geninterrupt(0x1a); cen=_CH; yrs=_CL; mons=_DH; days=_DL; cen = cen <<4; *((unsigned char )(&cen)) = (((unsigned char *)(&cen))) >>4; cen = cen + 0x3030;
mons = mons <<4; *((unsigned char )(&mons)) = (((unsigned char *)(&mons))) >>4; mons = mons + 0x3030;
yrs = yrs <<4; *((unsigned char )(&yrs)) = (((unsigned char *)(&yrs))) >>4; yrs = yrs + 0x3030;
days = days <<4; *((unsigned char )(&days)) = (((unsigned char *)(&days))) >>4; days = days + 0x3030;
clrscr();
printf("%c%c-%c%c-%c%c%c%c", (((unsigned char)(&days))+1), ((unsigned char)(&days)), (((unsigned char)(&mons))+1), ((unsigned char)(&mons)), (((unsigned char)(&cen))+1), ((unsigned char)(&cen)), (((unsigned char)(&yrs))+1), ((unsigned char)(&yrs))); getch(); }
Setting the Date
unsigned char ASCIItoBCD(char hi, char lo) { hi = hi - 0x30; lo = lo - 0x30; hi = hi << 4; hi = hi | lo; return hi; } void main () { unsigned char yrs,mons,days,cen; char ch1, ch2; puts("\nEnter the century to update: "); ch1=getche(); ch2=getche(); cen = ASCIItoBCD(ch1, ch2);
Another way to set Alarm
#include <bios.h> #include <dos.h> void interrupt newint70(); void interrupt (*oldint70)(); unsigned int far *scr = (unsigned int far *)0xb8000000; unsigned char ASCIItoBCD(char hi, char lo) { hi = hi - 0x30; lo = lo - 0x30; hi = hi << 4; hi = hi | lo; return hi; }
void main (void) { int temp; unsigned char hrs,mins,secs; char ch1, ch2;
puts("\nEnter the hours to update: "); ch1=getche(); ch2=getch(); hrs = ASCIItoBCD(ch1, ch2);
puts("\nEnter the minutes to update: "); ch1=getche(); ch2=getch(); mins = ASCIItoBCD(ch1, ch2);
puts("\nEnter the seconds to update: "); ch1=getche(); ch2=getch(); secs = ASCIItoBCD(ch1, ch2);
outportb(0x70,1); outportb(0x71,secs); outportb(0x70,3);
outportb(0x71,mins); outportb(0x70,5);
outportb(0x71,hrs); outportb(0x70,0x0b);
temp = inport(0x71); temp = temp | 0x70; outportb(0x70,0x0b); outportb(0x71,temp);
oldint70 = getvect(0x70); setvect(0x70, newint70); keep(0,1000); } void interrupt newint70() { outportb(0x70,0x0c); if (( inport(0x71) & 0x20) == 0x20) sound(0x21ff); scr=0x7041; (oldint70)(); }
This program takes the time of alarm as ASCII input which is firstly converted into BCD.
This BCD time is placed in the 64 byte RAM at the bytes which hold the alarm time.
Once the alarm time is loaded the register is accessed to enable the interrupts such that
other bits are not disturbed. Whenever the RTC generates an interrupt, the reason of the
interrupt needs to be established. This can be done by checking the value of status
register C, if the 5
th
bit of register C is set it indicates that the interrupt was generated
because the alarm time has been reached. The reason of interrupt generation is
established in the function newint70(). If the interrupt was generated because of alarm
then speaker is turned on by the sound() function and a character ‘A’ is displayed on the
upper left corner of the screen.
Determining Systems Information
INT 11H
INT 12H
INT 11H
used to get hardware environment info.
On Entry
call 11H
On Exit
AX = System Info.
Determining Systems Information
Interrupt 11H is used to determine the systems information. On return this service returns
the systems info in AX register. The detail of the information in AX register is shown in
the slide above.
