The IRQ and the address ranges for COM1, COM2, COM3 and COM4 are fixed.
However, if you wish to disable the port or change these parameters later you can do this in the system BIOS setup. The table overleaf shows the default settings for the panel PC’s serial ports.
COM1 and COM2 are one set. You can exchange the address range and interrupt IRQ of COM1 for the address range and interrupt IRQ of COM2. After exchanging:
COM1's address range is 2F8 ~ 2FF and its request IRQ is IRQ3. COM2's address range is 3F8 ~ 3FF and its interrupt IRQ is IRQ4.
COM3 and COM4 are another set. You can exchange the address range and interrupt IRQ of COM3 for the address range and interrupt IRQ of
COM4.
COM3’s address range is 3E8 ~ 3EF and its request IRQ is IRQ10. COM4’s address range is 2E8 ~ 2EF and its request IRQ is IRQ5.
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Table 4.5: Serial port default settings
Port | Address Range | Interrupt |
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COM1 | 3F8 ~ 3FF | IRQ4 |
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COM2 | 2F8 ~ 2FF | IRQ3 |
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COM3 | 3E8~3EF | IRQ10 |
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COM4 | 2E8~2EF | IRQ 5 |
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25 | Chapter4 |