TS code stream explanation
TS1 and TS2 ordered sets are a special packet format used in the PCIe (Peripheral Component Interconnect Express) protocol. These ordered sets are used for communication and control during the training phase of the PCIe link.
TS1 (Training Sequence 1) ordered set: TS1 ordered set is an 8-character long data packet used for initialization and synchronization at the beginning of link training.
TS2 (Training Sequence 2) ordered set: TS2 ordered set is a 32-character long data packet, which is used for further training and adjusting the parameters of the link to improve the reliability and performance of data transmission.
During the training process of the PCIe link, the sender and the receiver exchange ordered sets of TS1 and TS2 with each other to establish and optimize link communication. Specifically, they complete operations such as link initialization, parameter calibration, and adaptability through these ordered sets.
Therefore, TS1 and TS2 ordered sets are specific packet formats for link training and optimization in the PCIe protocol.
training sequence
The following is a translation of the image above:
The training sequence consists of an ordered set for initializing bit alignment, symbol alignment, and exchanging physical layer parameters.
Training sequences are special packets used for initialization and optimization during the training phase of a communication link. These packets are transmitted and exchanged in ordered sets.
During training, the main purpose of the training sequence is to:
Bit alignment: The ordered set in the training sequence helps the receiver determine the bit boundaries during link initialization, ensuring correct parsing and processing of the transmitted binary data.
Symbol alignment: Through the ordered set in the training sequence, the sender and receiver can achieve symbol alignment by identifying a specific sequence of symbols. This helps ensure that the receiver can accurately interpret the symbols transmitted by the sender.
Physical layer parameter exchange: Training sequences can also be used to exchange physical layer parameters during link initialization. By transmitting a specific ordered set, the sender and receiver can negotiate and set appropriate physical layer parameters to improve the reliability and performance of link transmission.
Through the use of ordered sets, the training sequence plays an important role in initializing bit alignment, symbol alignment and exchanging physical layer parameters in the link training phase. These actions help ensure that the link transmits data accurately and reliably.
Training sequences (TS1 or TS2) are transmitted continuously and can only be interrupted by SKP ordered sets (see § 4.2.7) or EIEOS ordered sets (see § 4.2.4.2) at other data rates.
During the training phase of the PCIe link, TS1 and TS2 ordered sets are continuously transmitted to establish and optimize link communication. This means that no other types of ordered sets or packets can be inserted during the transmission of the training sequence.
However, in specific cases, the transmission of training sequences can be interrupted by inserting SKP ordered sets or EIEOS ordered sets for other data rates. SKP ordered sets are typically used to fill idle slots or keep links alive. The EIEOS ordered set is a similar control sequence used when the data rate is not 2.5 GT/s.
Therefore, when the transmission of the training sequence is in progress, the continuous transmission of the training sequence can only be interrupted by inserting a SKP ordered set or an appropriate EIEOS ordered set. The existence of these ordered sets ensures that the link can be controlled and adjusted when needed.
In TS1 and TS2 ordered sets, the processing rules for reserved bits are as follows:
The sender (Transmitter) must set the reserved bits to 0 for transmission.
The receiver (Receiver) needs to process reserved bits according to the following rules:
The receiver cannot determine whether a TS1 or TS2 ordered set is invalid based on the value of the received reserved bit.
If reserved bits are included in the parity calculation, the receiver MUST use the received value of the reserved bits for the parity calculation.
For symbols (Symbols) that are explicitly required to be continuous in the TS1 or TS2 ordered set, the receiver may choose to compare the received reserved bit values to determine whether they are continuous.
The receiver cannot take any other functional action based on the value of the received reserved bits.
in other words:
The sender sets reserved bits to 0 during transmission.
When the receiver processes TS1 and TS2 ordered sets, it will not judge whether it is valid because of the value of the reserved bit.
If reserved bits are included in the parity calculation, the receiver uses the value of the received reserved bits for the calculation.
In symbols that specify that contiguousness is required, the receiver may choose to compare the received values of reserved bits.
Otherwise, the recipient will not take any other functional action based on the value of the received reserved bit.