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The standard port adresses are given below. Most PCs have them. If you are using IBM PS/2, equipped with a micro-channel bus, different addresses and interrupt requests can be expected. Just like LPT ports, base adresses for ÑÎÌ-ports can be obtained from the data range in BIOS.
| Name | Address | IRQ |
| COM 1 | 3F8 | 4 |
| COM 2 | 2F8 | 3 |
| COM 3 | 3E8 | 4 |
| COM 4 | 2E8 | 3 |
Standard Port Addresses
The table below contains the address having the addresses for COM-ports in BIOS data range. Each address has two bytes.
| Start Address | Function |
| 0000:0400 | COM1's Base Address |
| 0000:0402 | COM2's Base Address |
| 0000:0404 | COM3's Base Address |
| 0000:0406 | COM4's Base Address |
COM Port Addresses in the BIOS Data Area
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