Specifications

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2.6.5 Interrupt and DMA Channel Usage
The PC and AT buses provide a number of interrupt and DMA control signals. When you add
PC or AT bus plug-in cards which require either interrupt or DMA support, you must select
which channels of these functions will be used by the added card. This is typically done using
either switches or configuration jumpers on the plug-in card. It is important that you not
configure the added card to use an interrupt or DMA channel that is already being used! For
your convenience, Tables 2-19 and 2-20 provide a summary of the normal assignment of
interrupt and DMA channels on the Little Board/286.
Table 2-19. Interrupt Channel Assignment
INTERRUPT FUNCTION
IRQ0 ROM-BIOS clock tick function, from Timer 0
IRQ1 Keyboard controller output buffer full
IRQ2 Cascade input for IRQ8-15
IRQ3 Secondary serial port (if present)
IRQ4 Primary serial port (if present)
IRQ5 Reserved for secondary parallel printer
IRQ6 Floppy controller (if present)
IRQ7 Parallel printer (if present)
IRQ8 Battery-backed clock alarm
IRQ9 Available (corresponds to a PC’s IRQ2)
IRQ10 Available
IRQ11 Available
IRQ12 Available
IRQ13 80287 Math Coprocessor (if present)
IRQ14 Reserved for hard disk controller use
IRQ15 Available
Table 2-20. DMA Channel Assignment
CHANNEL FUNCTION
0 Available for 8-bit transfers
1 Available for 8 bit transfers
2 Floppy controller (if present)
3 Available for 8-bit transfers
4 Cascade for channels 0-3
5 Available for 16-bit transfers
6 Available for 16-bit transfers
7 SCSI controller (if present)