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An IRQ is an electrical signal generated by a device needing attention. Usually, it means that some event has occurred such as data being received and ready to use. The IRQ signal is sometimes connected directly to the processor or in some cases to a dedicated interrupt handling circuit. When the processor is told the interrupt has happened it calls the ISR to handle it.
The ISR is software that deals with the needs of the device that requested it. Usually, the device is read or some system action is taken to clear the condition that caused the IRQ then the interupt system is reset to make it ready for use again.
On most systems, the IRQ signal forces the processor to save it's current program counter so it knows where to return when the ISR is finished, then it jumps to a hard-wired address called the Interrupt Vector where the code for the ISR is placed. At the end of the ISR, the program counter is restored and the program carries on from where it was before the interrupt paused it.
Antonio Holl
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What IRQ does COM2 use?
IRQ 3.
What IRQ does LPT1 usually use?
LTP1 should use IRQ7.
Which two IRQ settings are connected together?
IRQ Ports 2 & 9 -Taylor
What system resources does com1 use com2 com2 com3 com4?
COM1-IRQ 4, memory addresses 03F8-03FF COM2-IRQ 3, memory addresses 02F8-02FF COM3-IRQ 4, memory addresses 03E8-03EF COM4-IRQ 3, memory addresses 02E8-02EF pg. 396
What IRQ does the system timer use?
0
Which IRQ has the highest priority?
15
What does an IRQ allow interface cards to do?
IRQ or interupt request : An IRQ allows a device to request certain system resources on priority. Normally, the system allowcates the different non-competing IRQ numbers to different devices. The system allocated IRQs may some times be manually changed. However, it may lead to serious IRQ conflicts resulting in a hung operating system.
What IRQ does COM2 use?
IRQ 3.
What IRQ does LPT1 usually use?
LTP1 should use IRQ7.
What is the IRQ for the floppy disk drive controller?
By default, the IRQ for the floppy disk controller is IRQ 6.
What is the Interrupt Request IRQ assigned to LPT1?
By default IRQ 7 is assigned to LPT1.
What is the address of COM1?
From: http://www.techadvice.com/tech/C/ComPort_TS.htmCom1, IRQ 4, address: 3F8Com2, IRQ 3, address: 2F8Com3, IRQ 4, address: 3E8Com4, IRQ 3, address: 2E8
What is the IRQ for a keyboard?
IRQ 1 is used exclusively for the keyboard controller.
What is the standard IRQ setting for the system time?
IRQ 1
List interrupts used with the IBM PC type sytems?
IRQ 0 - System timer. IRQ 1 - Keyboard. IRQ 2 - Cascaded signals from IRQs 8-15. IRQ 3 - COM2 (Default) and COM4 (User) serial ports IRQ 4 - COM1 (Default) and COM3 (User) serial ports IRQ 5 - LPT2 Parallel Port 2 or sound card IRQ 6 - Floppy disk controller IRQ 7 - LPT1 Parallel Port 1 or sound card (8-bit Sound Blaster and compatibles) IRQ 8 - Real time clock IRQ 9 - Free / Open interrupt / Available / SCSI. Any devices configured to use IRQ 2 will actually be using IRQ 9. IRQ 10 - Free IRQ 11 - Free IRQ 12 - PS/2 connector Mouse. IRQ 13 - ISA / Math Co-Processor IRQ 14 - Primary IDE. If no Primary IDE this can be changed IRQ 15 - Secondary IDE These are just a set of standard IRQs. For much more detail check our Ralf Brown's list located at http://www.cs.cmu.edu/~ralf/files.html
If more than on IRQ is up at the same time how does the interrupt controller select with to process first?
The priority of interrupts on the 8085 is, in order of decreasing priority, TRAP, RST7.5, RST6.5, RST5.5, and INTR. The priority of interrupts on the 8259 is dependent on the priority mode set by the programmer, it can either be 1.) fully nested mode, where IRQ0 has highest priority, 2.) auto rotation mode, where each has equal priority in a rotating scheme, and 3.) fixed rotation mode, where one is selected as highest by the programmer.
Which two IRQ settings are connected together?
IRQ Ports 2 & 9 -Taylor
