The physical properties of the bus system limit the amount of data that can be transmitted during one bus cycle. With Flatstream communication, all messages are viewed as part of a continuous data stream. Long data streams must be broken down into several fragments that are sent one after the other. To understand how the receiver puts these fragments back together to get the original information, it is important to understand the difference between a message, a segment, a sequence and an MTU.

总线系统的物理特性限制了一个总线周期内可传输的数据量。在Flatstream通信中，所有消息都被视为连续数据流的一部分。长的数据流必须被分解成几个片段，然后一个接一个地发送。为了理解接收方如何将这些片段重新组合起来以获得原始信息，理解消息、段、序列和MTU之间的区别是很重要的。

Message

消息

A message refers to information exchanged between 2 communicating partner stations. The length of a message is not restricted by the Flatstream communication method. Nevertheless, module-specific limitations must be considered.

消息是指两个通信伙伴站之间交换的信息。消息的长度不受Flatstream通信方法的限制。然而，必须考虑特定模块的限制。

Segment (logical division of a message):

段 (消息的逻辑划分):

A segment has a finite size and can be understood as a section of a message. The number of segments per message is arbitrary. So that the recipient can correctly reassemble the transferred segments, each segment is preceded by a byte with additional information. This control byte contains information such as the length of a segment and whether the approaching segment completes the message. This makes it possible for the receiving station to interpret the incoming data stream correctly.

段的大小是有限的，可以理解为消息的一部分。每条消息的分段数是任意的。为了使接收者能够正确地重新组装所传输的段，每个段前面都有一个带有附加信息的字节。这个控制字节包含一些信息，如段的长度和临近的段是否完成了消息之类的信息。这使得接收站有可能正确解释传入的数据流。

Sequence (how a segment must be arranged physically):

序列（段在物理必须如何排列）

The maximum size of a sequence corresponds to the number of enabled Rx or Tx bytes (later: "MTU"). The transmitting station splits the transmit array into valid sequences. These sequences are then written successively to the MTU and transferred to the receiving station where they are put back together again. The receiver stores the incoming sequences in a receive array, obtaining an image of the data stream in the process.

With Flatstream communication, the number of sequences sent are counted. Successfully transferred sequences must be acknowledged by the receiving station to ensure the integrity of the transfer.

序列的最大大小对应于启用的Rx或Tx字节数相对应（后文："MTU"）。发送站将发送阵列分割成有效序列。然后，这些序列被连续写入MTU并传输到接收站，在那里它们又被重新组合起来。接收站将传入的序列存储在一个接收阵列中，在此过程中获得数据流的图像。

使用Flatstream通信时，会对发送的序列数进行计数。成功传输的序列必须得到接收站的确认，以确保传输的完整性。

MTU (Maximum Transmission Unit) - Physical transport:

（最大传输单元）-物理传输：

MTU refers to the enabled USINT registers used with Flatstream. These registers can accept at least one sequence and transfer it to the receiving station. A separate MTU is defined for each direction of communication. OutputMTU defines the number of Flatstream Tx bytes, and InputMTU specifies the number of Flatstream Rx bytes. The MTUs are transported cyclically via the X2X Link network, increasing the load with each additional enabled USINT register.

MTU指的是与Flatstream一起使用的已启用的USINT寄存器。这些寄存器可以接受至少一个序列并将其传输到接收站。每个通信方向都定义了一个单独的MTU。OutputMTU定义了Flatstream Tx字节的数量，而InputMTU指定了Flatstream Rx字节的数量。MTU通过X2X Link网络循环传输，每增加一个启用的USINT寄存器就增加一个负载。

Properties

特点

Flatstream messages are not transferred cyclically or in 100% real time. Many bus cycles may be needed to transfer a particular message. Although the Rx and Tx registers are exchanged between the transmitter and the receiver cyclically, they are only processed further if explicitly accepted by register "InputSequence" or "OutputSequence".

Flatstream 信息不是循环传输的，也不是100%实时传输的。传输一个特定的消息可能需要许多总线周期。尽管Rx和Tx寄存器在发送器和接收器之间循环交换，但只有在寄存器 "InputSequence "或 "OutputSequence "明确接受的情况下才会进一步处理。

Behavior in the event of an error (brief summary)

发生错误时的行为（简述）

The protocol for X2X and POWERLINK networks specifies that the last valid values should be retained when disturbances occur. With conventional communication (cyclic/acyclic data queries), this type of error can generally be ignored.

In order for communication to also take place without errors using Flatstream, all of the sequences issued by the receiver must be acknowledged. If Forward functionality is not used, then subsequent communication is delayed for the length of the disturbance.

If Forward functionality is being used, the receiving station receives a transmission counter that is incremented twice. The receiver stops, i.e. it no longer returns any acknowledgments. The transmitting station uses SequenceAck to determine that the transmission was faulty and that all affected sequences must be repeated.

X2X和POWERLINK网络的协议规定，当发生干扰时，应保留最后的有效值。在传统的通讯中（循环/循环数据查询），这种类型的错误一般可以忽略不计。

为了使用Flatstream在没有错误的情况下进行通信，接收器发出的所有序列必须被确认。如果不使用转发功能，那么随后的通信将在干扰的长度内被延迟。

如果使用转发功能，接收站将收到一个递增两次的传输计数器。接收站停止，即它不再返回任何确认。发送站使用SequenceAck来确定传输是有问题的，并且必须重复所有受影响的序列。

消息、段、序列、MTU - Message, segment, sequence, MTU