IRQS: Hardware Interrupts
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`IRQS: Hardware Interrupts
`
`990verview99
`Devices such as the keyboard and disk controller are connected to the
`(IRQs). When these devices need
`CPU via Interrupt ReQuest lines
`servicing,
`they signal to the CPU which immediately begins executing
`code at a particular interrupt vector.
`
`00Standard IRQs90
`
`Oei
`
`IRQ
`
`0
`
`Timer
`
`INT 0911
`
`IRQ
`
`Keyboard
`
`INT Uafl
`
`IRQ
`
`cascade
`
`INT Obfl
`
`IRQ
`
`COM 2/4
`
`INT OCH
`
`COM 1/3
`
`LPT 2
`
`INT OGH
`
`IRQ
`
`diskette
`
`INT OfH
`
`IRQ
`
`LPT 1
`
`70H
`
`IRQ
`
`RT Clock
`
`INT 71H
`
`IRQ
`
`redir IRQ2
`
`Interrupts every 55ms
`
`(18.2 times per second)
`
`Interrupts on each press and release of a key
`and periodically while the key is held down.
`See Keyboard Ports.
`
`Connected to the secondary 8259a interrupt
`controller on ATs; may be used by EGA for
`vertical retrace.
`See EGA I/O Ports.
`
`Interrupts when COM2 or COM4 has something to
`say.
`See §§riai Ports.
`
`Interrupts when COMI or COM3 has something to
`say.
`See Serial Ports.
`
`AT: Interrupts when the printer on LPT2 is ready
`for another character
`(only if printer port 27aH
`See Printer Ports.
`
`is set up for this).
`
`PC/XT: This was used for the hard disk.
`XT Hard Disk Ports.
`
`See
`
`Interrupts after each action of the floppy
`diskette controller (read, write, seek, etc).
`See FDC Ports.
`
`Interrupts when LPT1 is ready for another
`character
`(only when controller port 37aH is set
`up for this).
`See Printer Ports.
`
`(on AT~class or
`Interrupts 1024 times per second
`better computers). This is generated by the
`same hardware that handles the non—volatile data
`
`in the CMOS Memory.
`
`IRQ 2 is used as the
`On AT-class computers,
`connection to a secondary 8259a interrupt
`controller. Actual occurrences of IRQ 2 are
`redirected to IRQ 9.
`This IRQ may be generated
`by EGA/VGA.
`See EGA I/O Ports.
`
`INT
`INT
`INT
`
`72H
`73H
`74H
`
`IRQ
`IRQ
`IRQ
`
`10
`ll
`12
`
`(reserved)
`(reserved)
`(reserved)
`
`There is no default device for
`There is no default device for
`There is no default device for
`
`this IRQ.
`this IRQ.
`this IRQ.
`
`42%»
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`I
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`Hardware Intenupts
`
`
`
`http://wehpaéges.chaxrer.net/danroliins/fegh1ie1f5}8096.I-ITM
`
`TNT 75H IRQ 13 math chip
`
`The 80x87 math coprocessor generates this
`interrupt on exceptions (errors).
`
`INT 761-I
`
`IRQ 14 hard disk
`
`Interrupts when the hard disk controller
`finishes an operation.
`See 1'-\'1‘ Hard Dis}: Ports_.
`
`INT 771-I
`
`IRQ 15
`
`(reserved) There is no default device for this IRQ.
`
`See Also:
`
`Intet1'L1pL.s and E105 Services
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