1, motherboard serial port 1 default value: 3F8/IRQ4 automatic: automatically set by BIOS. 3F8/IRQ4 specifies the serial port 1 as COM 1, uses interrupt 4, and the I/Q port address is 3f8; Disabled: Turn off the serial port 1 on the motherboard. Options: 2f8/irq3; ; 3e 8/IRQ 4； 2E8 / IRQ3 .
2. The default value of motherboard serial port 2 is: 2F8/IRQ3 address is 2F8, and interrupt is 3; Automatic: set automatically by BIOS: Disabled: Close the serial port on the motherboard 2. Select the same as above.
3. Default value of built-in parallel interface: 378/IRQ7 interrupt 7, and I/O address is 378; Disabled: Close the parallel port on the motherboard; 3BC/IRQ7, using the parallel port on the motherboard, and specifying interrupt 7, with the I/Q address 3bc; 278 / IRQ .
Extended data:
The CPU controls the external devices through the interface in the following ways:
1, program query mode
In this way, the CPU queries the current state of the specified peripheral through I/O instructions. If the peripheral device is ready, it will input or output data, otherwise the CPU will wait and loop the query.
The advantage of this method is simple structure and only a few hardware circuits are needed. The disadvantage is that the speed of CPU is much higher than that of peripheral devices, and it is usually in a waiting state, so the work efficiency is very low.
2. Interrupt handling
So the CPU can execute other programs instead of waiting passively. Once the peripheral device is ready for data exchange, it can submit a service request to the CPU. If the CPU responds to this request, it will temporarily stop the execution of the current program. To execute the service program corresponding to the request, please continue to execute the initially interrupted program after completion.
The advantages of the interrupt handling method are obvious. It not only saves the time required for CPU to query the status of peripheral devices and wait for peripheral devices to be ready, but also improves the working efficiency of CPU and meets the real-time requirements of peripheral devices.