Technical Note #1553

Standard COM Port Addresses and IRQs

Application affected:	General Hardware	Date Created:	9/25/96
Version Number:	n/a	Last Modified:	9/25/96
File Date(s):	n/a	Created By:	Mike Rimov
Type of Note:	Technical Guide	Additional Info:

Keywords: IRQ Addresses com port serial base address

Summary:

It can be confusing at times and difficult to remember each of the COM port base addresses, and IRQs.

This technical note provides a handy table which lists each of the addresses and IRQs in a easy to read chart.

 

Details:

These are the following standard Communications Port base addresses and IRQ's. These may be modified, but they are a good place to start on many systems:

COM Port	Base Address	IRQ
1	03F8	4
2	02F8	3
3	03E8	4
4	02E8	3

As can be seen from the table above, COM1 and COM3 share the same IRQ and COM2 and COM4 share the same IRQs by default. If the mouse and modem are on the same IRQ, then as soon as the Modem port is accessed, the computer will stop receiving messages from the mouse until the port is closed.

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