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Application Note 6

Base Address, IRQ, and DMA Channel Usage

Applies to: SIGNAL & RTS

NOTE: This note applies only to DT-2821 and DART PCMCIA

analog I/O boards.

Overview

Add-in hardware boards, such as analog I/O, DSP, SCSI controller, etc. are internally set to

utilize a particular base address, interrupt level (IRQ), DMA channel, and/or ROM address.

Base address sets the address through which the computer communicates with control

registers on the board. Typical base addresses lie between 200 and 3f0 hex, and most boards

occupy several addresses following the base, e.g., 240-24f hex (see the following table).

Interrupt level (IRQ) indicates which interrupt channel will be used by the board to request

interrupt service from the computer. IRQ channels are numbered 1 - 15 (decimal). DMA

channel indicates which DMA (Direct Memory Access) channel will be used by the board to

request DMA service. DMA channels are numbered 0 - 3 and 5 - 7. ROM address applies

only to bootable controller boards, and indicates where the board's BIOS code is installed in

the computer's memory. ROM addresses typically run in range c0000 - dffff (hex).

Hardware conflicts can arise when two different boards are set to the same base address,

IRQ, DMA channel, or ROM address. These conflicts can cause the system to malfunction

or even not boot. Boards should never share a base address, IRQ, DMA channel, or

ROM address setting. Note that since a base address is really an address range (see the

table), no part of that range may overlap another board's. Conflicts are resolved by

determining the address/IRQ/DMA assignments of all boards in the system and altering these

assignments to eliminate the overlap. This may involve changing both the board, through

jumpers or software, and its controlling software, such as SIGNAL.CFG for the SIGNAL

analog I/O board.

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Engineering Design NIDisk Guia do Utilizador Página 13