[AUTOSAR cantp 1. learn the network layer protocol of UDS diagnosis]

Interpretation of nouns

• DL： The length of valid data , barring PCIbyte;
• FS： Indicates whether the sender can continue to transmit messages ,0 Indicates that you can continue sending ,1 It means waiting for sending ,2 Indicates data overflow , The data sent at one time is greater than the amount that the receiver can receive ;
• BS： The receiver can receive the largest amount of data at a time ;
• STmin： Represents the minimum time interval between two consecutive frames , Refer to the picture 1 Defined in the ;
• SN： Serial number of consecutive frames
• N_As： The maximum time for the sender to transmit data to the receiver .
• N_Bs： The maximum time between the sender sending the first frame successfully and receiving the flow control frame .
• N_Br： The maximum time from the receiving end to the transmission flow control after receiving the first frame .
• N_Ar： The maximum time for the receiving end to transmit flow control to the sending end .
• N_Cr： The maximum time between the receiving end successfully sending flow control and receiving continuous frames .
• Ttan： Transmission time per frame .

Frame category

For the type of frame , It is determined by the length of data to be sent . In normal addressing mode , When the data length is less than or equal to 7byte, Then send it in the form of a single frame , When the data length is greater than 7byte, Data needs to be sent in multiple frames , You need to use the first frame 、 Flow control frame 、 Consecutive frames , The mechanism of different frames is shown in the figure 2 Shown .

The first frame refers to the first frame sent , The purpose is to front 7byte Send the data to the receiver , And inform the receiver that the data has not been sent , Then the receiver will return a flow control frame , Inform the sender whether it can continue to send , And inform the receiver of the maximum amount of data that can be received at one time , And the next data frame sent by the sender ( Consecutive frames ) The time interval between （STmin）.

For different frames , adopt CAN Message data field PCI（Protocol control information） To distinguish between , chart 3、 chart 4 Details of different frames PCI The definition of .

The following is right PCI Detailed explanation of paragraph .

A single frame ：

    When N_PCItype = 0 when , Indicates that this frame is a single frame ,SF_DL For the amount of data transmitted in a single packet .

First frame ：

    When N_PCItype = 1 when , Indicates the first frame of this frame ,FF_DL For the amount of data transmitted in this multi packet ,FF_DL The maximum value of is 4095.

Sequence frame ：

    When N_PCItype = 2 when , Indicates that this frame is a sequence frame ,SN Is the count of sequence frames , For orderly transmission of data , First send SN The value of is 1, When SN When the value of overflows ,SN from 0 Start counting .

Flow control frame ：

    When N_PCItype = 3 when , Indicates that this frame is a flow control frame ,FS Status information transmitted for data flow ,BS The interval between sending flow control frames for the receiver （ With CF In frames ）,ST The time interval between sending sequence frames for the sender .

When FS=0 when , On behalf of the receiver, data transmission is ready , The sender can send sequence frames ; When FS=1 when , The sender Continue to wait for the flow control frame and reset N_BS Timeout timer ; When FS=2 when , The memory on behalf of the receiver is not enough to receive FF_DL Length data , The sender ends the data transmission . When BS=0 when , The receiver will no longer send flow control frames , The sender can send the sequence frame until the data transmission is completed .

among ：

DL： The length of valid data , barring PCIbyte;

FS： Indicates whether the sender can continue to transmit messages ,0 Indicates that you can continue sending ,1 It means waiting for sending ,2 Indicates data overflow , The data sent at one time is greater than the amount that the receiver can receive ;

BS： The receiver can receive the largest amount of data at a time ;

STmin： Represents the minimum time interval between two consecutive frames , Refer to the picture 1 Defined in the ;

SN： Serial number of consecutive frames

Network layer diagnosis time analysis

The time management of the network layer is to ensure that the sender and receiver will not be permanently suspended because of waiting , Thus losing the ability of communication . Therefore, the timeout time parameter is set during each call .

Time relation N_BS = N_AR+N_BR
N_AS
N_CR

N_As： The maximum time for the sender to transmit data to the receiver .

N_Bs： The maximum time between the sender sending the first frame successfully and receiving the flow control frame .

N_Br： The maximum time from the receiving end to the transmission flow control after receiving the first frame .

N_Ar： The maximum time for the receiving end to transmit flow control to the sending end .

N_Cr： The maximum time between the receiving end successfully sending flow control and receiving continuous frames .

Ttan： Transmission time per frame .

STmin： The minimum transmission interval between two consecutive frames .

N_As、N_Bs、N_Cr、Ttan In practical application, it is a fixed value , Therefore, in multi frame transmission ,STmin Parameters have an important influence on the time of multi frame transmission .

The process of sending and receiving

ISO-15765 Official network sequence diagram

The definition and timeout of its time parameters are as follows