Components of the Ethernet Card: MAC/PHY/Transformer

The hardware components of the Ethernet Card are MAC/PHY/transformer/EEPROM.

On our platform, Mac is generally integrated into the master. The PHY and the transformer are separated. (Because PHY simulates differential signals externally and integrates a large number of analog hardware, Mac is a typical full digital device. Chip area and analog/digital hybrid architecture are the reasons why Mac is first integrated into the microcontroller and PHY is left off the chip. The more flexible and higher-density chip technology can already achieve single-chip integration between MAC and PHY .)

1
Ethernet interfaces can be divided into the protocol layer and the physical layer.
The protocol layer is composedMAC (media access layer)Single module implementation of the controller. Corresponds to the data link layer of the OSI Layer-7 model.
The physical layer consists of two parts,Namely, the physical layer andTransmitter. Corresponds to the physical layer of the OSI Layer-7 model.

The physical layer defines the electrical signal level conversion, line status, clock reference, and data encoding required for data transmission and receiving, and provides standard interfaces to the data link layer equipment.
The data link layer provides addressing mechanisms, data frame construction, data error check, transfer control, and standard data interfaces to the network layer.

2
There is also a Network Transformer between PHY and RJ45, also known as the data pump, which is a device on the consumption-level PCI Nic. The data pump is also called a Network Transformer or a network isolation transformer.
It plays two main roles on one network card:
The first is data transmission. It filters the differential signal sent by the PHY using the difference mode coupled coil coupling to enhance the signal, and coupling to the other end of the Connection Network at different levels through the electromagnetic field conversion;
The first is to isolate the different levels of different network devices connected by the network cable, so as to prevent the transmission of different voltages from damaging the device through the network cable. In addition, data mercury can also protect the equipment against lightning.

Role of network isolation Transformer in Ethernet [from Baidu encyclopedia]
What is the role of this transformer? Can it be left alone. Theoretically, transformer can be directly connected to RJ45 without being connected. However, the transmission distance is very limited, and when connected to different levels of Network Ports, it will also affect. In addition, the external interference to the chip is also great. After the network transformer is connected, it filters the differential signal sent by PHY with the difference mode coupling coil to enhance the signal, and coupling to the other end of the connected network through the electromagnetic field conversion. In this way, not only does the network cable and the PHY have no physical connection, but the signal is transferred instead, the DC component in the signal is cut off, and data can be transmitted in devices of different 0 V levels.
First, the signal can be enhanced to make the transmission distance farther;
Second, the chip end is isolated from the outside, and the anti-interference capability is greatly enhanced, and the chip is greatly protected (such as lightning strikes );
Third, when connected to a network port of different levels (for example, some PHY chips are 2.5 V and some PHY chips are 3.3 V), they will not affect each other's devices.

3
If there is no integration, you still needOne EEPROM Chip, Usually a 93c46. It records the NIC chip supplier ID, subsystem supplier ID, Nic MAC address, Nic configurations, such as the PHY address on the SMI bus and bootrom capacity, whether to enable the bootrom boot system.

Introduction to layer-7 OSI models:
Level 1: Physical Layer
Responsible for encoding the information into current pulses or other signals for online transmission. It consists of the actual interface between the computer and the network medium, can define electrical signals, symbols, line status and clock requirements, data encoding and data transmission connector. Such as the most commonly used RS-232 specification, 10base-t Manchester code and RJ-45 belongs to the first layer. All layers higher than the physical layer communicate with it through predefined interfaces. For example, the Ethernet ancillary unit interface (AUI), a DB-15 connector can be used to connect Layer 1 and Layer 2.
Layer 2: Data Link Layer
Provides reliable data transmission through physical network links. Different data link layers define different network and Protocol features, including physical addressing, network topology, error verification, frame sequence, and traffic control. The physical addressing (corresponding to the network addressing) defines the addressing method of the device at the data link layer. The network topology defines the physical connection mode of the device, such as the bus topology and the ring topology; error verification sends an alarm to the upper-layer protocol when a transmission error occurs. The data frame sequence is reorganized and frames other than the sequence are transmitted. throttling may delay data transmission, in this way, the receiving device will not crash because it receives information that exceeds its processing capability at a certain time point. The data link layer is actually composed of two independent parts: Media Access
Control, Mac) and Logical Link Control (LLC ). Mac describes how to schedule, generate, and receive data on a site in a shared media environment. Mac ensures reliable cross-link information transmission, synchronizes data transmission, and identifies errors and controls data flow. Generally, Mac is only important in the shared media environment. Only nodes in the shared media environment can be connected to the same transmission media. The ieee mac rule defines an address to identify multiple devices in the data link layer. The Logical Link Control Sub-layer manages the communication between devices on a single network link. IEEE 802.2 standard defines LLC. LLC supports connectionless services and connection-oriented services. Many domains are defined in the Information frames at the data link layer. These domains allow multiple high-level protocols to share one physical data.
Link.
Layer 3: Network Layer
Establishes connections between source and end points. It generally includes network path finding, and may also include traffic control and error checks. Data transmission between different network segments of the same mac standard generally only involves the data link layer, while data transmission between different MAC standards involves the network layer. For example, an IP router works at the network layer, and thus multiple networks can be interconnected.
Layer 4: Transport Layer
Provides reliable end-to-end network data flow services to the top management. The functions of the transport layer generally include flow control, multi-channel transmission, virtual circuit management, error checksum and recovery. Traffic control manages data transmission between devices to ensure that the transmission is not able to send data that is larger than the processing capability of the receiving device; multi-channel transmission allows data of multiple applications to be transmitted to one physical link. virtual circuits are established, maintained, and terminated by the transport layer; error verification includes different structures established to detect transfer errors, and error recovery includes actions (such as request data re-transmission) to resolve any errors. Transport Control Protocol (TCP) is a transport layer protocol in the TCP/IP protocol family that provides reliable data transmission.
Layer 5: Session Layer
Establishes, manages, and terminates communication sessions between the presentation layer and the entity. Communication sessions include service requests and service responses that occur between different network application layers. These requests and responses are implemented through the Session Layer Protocol. It also includes creating checkpoints so that a previous status can be returned when communication is interrupted.
Layer 6: Presentation Layer
Multiple functions are provided for data encoding and conversion at the application layer to ensure that information sent at the application layer of one system can be identified by the application layer of another system. The encoding and conversion modes of the presentation layer include public data representation format, performance conversion representation format, public data compression mode, and public data encryption mode.
The common data representation format is the standard image, sound, and video format. By using these standard formats, different types of computer systems can exchange data. The conversion mode exchanges information between systems by using different text and data table representations, for example, ASCII (American Standard Code for information interchange); standard data compression mode ensures that the compressed data on the original device can be properly decompressed on the target device; the encryption mode ensures that the encrypted data on the original device can be correctly decrypted on the target device.
The presentation layer protocol is generally not associated with a special protocol stack. For example, QuickTime is the video and audio standard of the applet computer, and MPEG is the ISO video compression and encoding standard. Common image formats such as PCX, GIF, and JPEG are different static image compression and encoding standards.
Layer 7: Application Layer
It is closest to the end user's OSI layer, which means that the OSI Application Layer interacts directly with users through application software. Note: The application layer is not composed of actual application software running on the computer, but composed of APIs that provide the application with access to network resources, such applications are beyond the scope of the OSI model. The functions of the application layer generally include identifying communication partners, defining resource availability and synchronous communication. As the communication partner may be lost, the application layer must define the identification and availability of the communication partner for the Application subroutine that transmits data. When defining resource availability, the application layer must determine whether there is sufficient network resources for communication requests.
Source. In synchronous communication, communications between all applications require collaborative operation at the application layer.
OSI application layer protocols include file transmission, access and management protocols (FTAM), file virtual terminal protocol (VIP), and public management system information (CMIP.