COM interface:
COM interface is also called serial port. In the past, most motherboards provided two COM interfaces, COM1 and COM2. The role of the COM interface is to connect devices such as serial mice and external modems. The 1/O address of the COM1 interface is 03F8h-03FFh, and the interrupt number is IRQ4: The 1O address of the COM2 interface is O2F8h-O2Fh, and the interrupt number is IRQ3. Therefore, the COM2 interface has priority over the response of the COM1 interface. Later, serial port devices such as mice used PS2 interfaces and currently popular USB interfaces, and external devices based on serial ports are rare.
USB interface:
The full name of USB is Universal Serial Bus, which Chinese means "Universal Serial Bus". USB was jointly proposed by Intel, Compaq, IBM, Microsoft and other companies at the end of 1994. USB supports hot-plug press, and its plug-and-play advantages make it the most important interface way for computers.
The USB interface has 4 pins, which are USB power supply (usually 5V), USB data cable +, USB data cable and ground wire.
USB has two specifications, USBI.1 and USB2.0.
The transmission rate of USBI.1 is 12 Mbit/s for the high-speed mode, and 1.5 Mbit/s for the low-speed mode, 1Mb/s=8 Mbit/s, and 12 Mbit/s=l .5 MB/s.
The USB 2.0 specification is an evolution of the USBI.1 specification. Its transfer rate reaches 480Mbit/s, which translates to 60MB/s, which is enough to meet the speed requirements of most peripherals. The Enhanced Host Controller Interface (EHCI) in USB 2.0 defines a USB 1.1-compatible architecture that can drive USB.1 devices with USB 2.0 actuators. In other words, all devices that support USB1.1 can be used directly on the USB2.0 interface without worrying about compatibility issues, and accessories such as USB cables and plugs can also be used directly.
The USB2.0 standard further increases the interface rate to 480Mbit/s, which greatly shortens the transmission time of video and audio files in LCD color TVs.
Type-C interface:
Type-c is an interface type that can be applied to both a PC (master) and an external device (slave such as a mobile phone), which is epoch-making.
Micro-USB interface:
Micro-USB is a USB 2.0 standard interface that is the next version of Mini-USB. Its features are as follows:
Micro-USB connectors are smaller and space-saving than standard USB and Mini-USB connectors;
With up to 10,000 mating cycles and strength;
Blind mating structure design;
Compatible with USB1.1 (low speed: 1.5 Mbit/s, full speed: 12 Mbit/s) and USB2.0 (high speed: 180 Mbit/s);
Provides both data transfer and charging.
