How to write C program for 8259 controller -

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i working on interrupts. have understand how use 8259 pic. can guide me how write program in c it. (i worked on 8051) suppose can used 8051.

this set of definitions common rest of section. outb(), inb() , io_wait() functions, see page.

#define pic1        0x20        /* io base address master pic */ #define pic2        0xa0        /* io base address slave pic */ #define pic1_command    pic1 #define pic1_data   (pic1+1) #define pic2_command    pic2 #define pic2_data   (pic2+1)

perhaps common command issued pic chips end of interrupt (eoi) command (code 0x20). issued pic chips @ end of irq-based interrupt routine. if irq came master pic, sufficient issue command master pic; if irq came slave pic, necessary issue command both pic chips.

#define pic_eoi     0x20        /* end-of-interrupt command code */  void pic_sendeoi(unsigned char irq) {     if(irq >= 8)         outb(pic2_command,pic_eoi);      outb(pic1_command,pic_eoi); }

when enter protected mode (or before hand, if you're not using grub) first command need give 2 pics initialise command (code 0x11). command makes pic wait 3 "initialisation words" on data port. these bytes give pic:

  1. its vector offset. (icw2)
  2. tell how wired master/slaves. (icw3)
  3. gives additional information environment. (icw4)
#define icw1_icw4 0x01        /* icw4 (not) needed */ #define icw1_single   0x02        /* single (cascade) mode */ #define icw1_interval4    0x04        /* call address interval 4 (8) */ #define icw1_level    0x08        /* level triggered (edge) mode */ #define icw1_init 0x10        /* initialization - required! */  #define icw4_8086 0x01        /* 8086/88 (mcs-80/85) mode */ #define icw4_auto 0x02        /* auto (normal) eoi */ #define icw4_buf_slave    0x08        /* buffered mode/slave */ #define icw4_buf_master   0x0c        /* buffered mode/master */ #define icw4_sfnm 0x10        /* special nested (not) */ 
void pic_remap(int offset1, int offset2) {     unsigned char a1, a2;      a1 = inb(pic1_data);                        // save masks     a2 = inb(pic2_data);      outb(pic1_command, icw1_init+icw1_icw4);  // starts initialization sequence (in cascade mode)     io_wait();     outb(pic2_command, icw1_init+icw1_icw4);     io_wait();     outb(pic1_data, offset1);                 // icw2: master pic vector offset     io_wait();     outb(pic2_data, offset2);                 // icw2: slave pic vector offset     io_wait();     outb(pic1_data, 4);                       // icw3: tell master pic there slave pic @ irq2 (0000 0100)     io_wait();     outb(pic2_data, 2);                       // icw3: tell slave pic cascade identity (0000 0010)     io_wait();      outb(pic1_data, icw4_8086);     io_wait();     outb(pic2_data, icw4_8086);     io_wait();      outb(pic1_data, a1);   // restore saved masks.     outb(pic2_data, a2); }

for masking

void irq_set_mask(unsigned char irqline) {     uint16_t port;     uint8_t value;      if(irqline < 8) {         port = pic1_data;     } else {         port = pic2_data;         irqline -= 8;     }     value = inb(port) | (1 << irqline);     outb(port, value);         }  void irq_clear_mask(unsigned char irqline) {     uint16_t port;     uint8_t value;      if(irqline < 8) {         port = pic1_data;     } else {         port = pic2_data;         irqline -= 8;     }     value = inb(port) & ~(1 << irqline);     outb(port, value);         }

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