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Which BIOS interrupt provides serial port services andlist down names of 9 pins of DB-9connector.

User Nalply
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Answer:

To help interrupt serial driven communications, the PC utilizes two interrupts, IRQ 3 and IRQ 4.

INT 0Bh and INT 0Ch are the BIOS interrupt

It patches the COM1,COM2 when you call the Com Init Intr routine: interrupt vectors (int 0Ch int 0Bh), allowing IRQ 4 and IRQ3 in the 8259A PIC.

IRQ 3 0Bh Serial port 2

IRQ 4 0Ch Serial port 1

9 pins of DB-9 connector -

1 RTS, Request to Send

2 CTS, Clear to send

3 GND,Ground

4 RXD,Receive Data

5 TXD, Transmit Data

6 DTR, Data Terminal Ready

7 DSR, Data Set Ready

8 RI, Ring Indicator

9 DCD,Data carrier detect

User David Schoonover
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