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What is PCIe Equalization?
Equalization is a method of distorting the data signal with a transform representing an approximate inverse of the channel response. It may be applied either at the Tx, the Rx, or both. A simple form of equalization is Tx de-emphasis as specified in PCIe 1.
What is PCIe de-emphasis?
PCIe uses transmit de-emphasis to compensate for high-frequency channel losses. A de-emphasized waveform is defined in terms of the voltage levels Va (de-emphasis) and Vb (flat level). Figure 3 shows the resultant output signal when a binary input stream is applied to a 3-tap FIR filter.
What is TS1 and TS2 in PCIe?
Refer the “PCIe Express Base Spec Ver 4.0.” D. TS1 & TS2: TS1 and TS2 are the training sequences used by both the devices doing link training to communicate the capabilities. As explained before, equalization also uses bits inside symbols of TS Ordered sets.
Why does PCIe have so many ground pins?
The extra pin for a common ground is needed so that the other computer knows what to compare the data signal with. The receive and transmit lines are crossed, so that data transmitted by computer 1 is received on the receive pin in computer 2.
How does PCIe equalization work?
It aims to provide 8GT/s bit rate across the same copper channel, almost doubling the data throughput over PCIe Gen 2.0. In Equalization, the signal is passed through a Filter having its frequency response equal to inverse of frequency response of the channel.
What is PCIe link training?
Link initialization and training is a Physical Layer control process that configures and initializes a device’s Physical Layer, port, and associated Link so that normal packet traffic can proceed on the Link. This process is automatically initiated after reset without any software involvement.
What is a PCIe channel?
PCIe or Peripheral Component Interconnect Express is a type of interface that allows high-speed components like graphics cards, SSDs, and WiFi cards to connect to your computer. Typical PCIe connectors take the form of expansion slots on the motherboard, allowing you to physically attach a supported device.
How does PCIe enumeration work?
During the enumeration process the system software discovers all of the switch and endpoint devices that are connected to the system, determines the memory requirements and then configures the PCIe devices. The enumeration process selects the bus numbers for each device that has a connection.
What is the purpose of link equalization in PCIe?
The Link equalization procedure enables components to adjust the Transmitter and the Receiver setup of each Lane to improve the signal quality (good eye). The equalization procedure can be initiated either autonomously or by software. Equalization has 4 phases, where phase 2&3 optional.
How many phases are there in PCIe equalization?
The equalization procedure can be initiated either autonomously or by software. Equalization has 4 phases, where phase 2&3 optional. Basically as part of equalization the pcie device tries to fine tune the transmitter (TX) of device connected at the other end.
When does phase 0 start in PCIe 3.0?
A starting-point preset is the entry to further tuning of the link, so the system provides that to the add-in card while still at 2.5 GT/s. Phase 0 starts at a rate of 2.5 GT/s. The system (upstream) sends a speed-change request along with a TxEQ preset to the add-in card (downstream).
What happens when PCIe link up is enabled?
Basically as part of equalization the pcie device tries to fine tune the transmitter (TX) of device connected at the other end. When the LTSSM is enabled, initially the PCIe link up will happen in GEN1 and then try to change the link speed to maximum supported speed.