What are ordered sets in PCIe?
Physical Layer Packets (PLPs), referred to as Ordered-Sets, are exchanged between neighboring devices during the Link training and initialization process. These packets were briefly described in the section on “Ordered-Sets” on page 433.
What is electrical idle in PCIe?
Electrical Idle indicates when a link has entered a temporarily inactive state (quiesed) and can herald entry/exit into low power states and link speed changes. To be PCIe compliant, the link transmitter must both be in a static state and also hold the transmission line to a fixed com- mon mode.
How flow control works in PCIe?
Credit-based flow control is point-to-point based, not end-to-end. Receiver sends Flow Control Packets (FCP) which are a type of DLLP (Data Link Layer Packet) to provide the transmitter with credits so that it can transmit packets to the receiver.
What is equalization in PCIe?
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. x and PCIe 2.
Why do we use scrambling in PCIe?
Data Scrambling – PCI Express employs a technique called data scrambling to reduce the possibility of electrical resonances on the link. PCI Express specification defines a scrambling/descrambling algorithm that is implemented using a linear feedback shift register.
What is Ltssm in PCIe?
The LTSSM (Link Training and Status State Machine) block checks and memorizes what is received on each lane, determines what should be transmitted on each lane and transitions from one state to another.
What is hot reset in PCIE?
A ‘hot reset’ is a conventional reset that is triggered across a PCI express link. A hot reset is triggered either when a link is forced into electrical idle or by sending TS1 and TS2 ordered sets with the hot reset bit set.
Which layer of PCIe has flow control mechanism?
the data link layer
As mentioned before, the data link layer has a Flow Control (FC) mechanism, which makes sure that a TLP is transmitted only when the link partner has enough buffer space to accept it.
What is virtual channel in PCIe?
VC (Virtual Channel) is a mechanism defined by the PCI Express standard for differential bandwidth allocation. Virtual channels have dedicated physical resources (buffering, flow control management, etc.) across the hierarchy.
What is de-emphasis in PCIe?
De-Emphasis and Pre-Shoot 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 the difference between scrambling and encryption?
Scrambling is generating a 48-bit secret key called control word for the data stream . And Encryption is used to protect the control word during transmission to the receiver: the control word is encrypted as an entitlement control message (ECM).
How does scrambled work?
Scrambling is accomplished by the addition of components to the original signal or the changing of some important component of the original signal in order to make extraction of the original signal difficult.