The NIC is equipped with processors and memory (including RAM and ROM). The communication between the network card and the LAN is carried through the serial transmission through the cable or twisted pair, while the communication between the network card and the computer is carried out by the I/O bus on the computer motherboard in parallel transmission. Therefore, an important function of the network card is to carry out serial/parallel conversions. Because the data rate on the network is not the same as the data rate on the computer bus, the storage chips that are cached for the data must be installed in the NIC.
When installing the network card, the device driver for the management network adapter must be installed on the computer's operating system, and the driver will tell the NIC that the block of data transmitted over the LAN should be stored in the location of the memory. The NIC is also able to implement Ethernet protocols.
The NIC is not a stand-alone autonomous unit because the NIC itself does not have a power supply but must use the computer that is plugged in and is controlled by the computer, so the NIC can be seen as a semi-autonomous unit. When the NIC receives a wrong frame, it discards the frame without notifying the computer it is inserting. When the NIC receives a correct frame, it uses the interrupt to notify the computer and deliver it to the network layer in the protocol stack. When the computer sends an IP datagram, it is handed down to the network adapter by the protocol stack and sent to the LAN.