Commission Implementing Regulation (EU) 2016/799Show full title

4. COMMUNICATION SERVICES U.K.

Some services are necessary to establish and maintain communication. They do not appear on the application layer. The services available are detailed in the following table:

Table 2

Communication Services

Service name	Description
StartCommunication	The client requests to start a communication session with a server(s).
StopCommunication	The client requests to stop the current communication session.
TesterPresent	The client indicates to the server that it is still present.

CPR_005 The StartCommunication Service is used for starting a communication. In order to perform any service, communication must be initialised and the communication parameters need to be appropriate for the desired mode. U.K.

4.1. StartCommunication Service U.K.

CPR_006 Upon receiving a StartCommunication indication primitive, the VU shall check if the requested communication link can be initialised under the present conditions. Valid conditions for the initialisation of a communication link are described in document ISO 14230-2. U.K.

CPR_007 Then the VU shall perform all actions necessary to initialise the communication link and send a StartCommunication response primitive with the Positive Response parameters selected. U.K.

CPR_008 If a VU that is already initialised (and has entered any diagnostic session) receives a new StartCommunication Request (e.g. due to error recovery in the tester) the request shall be accepted and the VU shall be reinitialised. U.K.

CPR_009 If the communication link cannot be initialised for any reason, the VU shall continue operating as it was immediately prior to the attempt to initialise the communication link.. U.K.

CPR_010 The StartCommunication Request message must be physically addressed. U.K.

CPR_011 Initialising the VU for services is performed through a ‘fast initialisation’ method, U.K.

• There is a bus-idle time prior to any activity.

• The tester then sends an initialisation pattern.

• All information which is necessary to establish communication is contained in the response of the VU.

CPR_012 After completion of the initialisation, U.K.

• All communication parameters are set to values defined in Table 4 according to the key bytes.

• The VU is waiting for the first request of the tester.

• The VU is in the default diagnostic mode, i.e. StandardDiagnosticSession.

• The calibration I/O signal line is in the default state, i.e. disabled state.

CPR_014 The data rate on the K-line shall be 10 400 Baud. U.K.

CPR_016 The fast initialisation is started by the tester transmitting a Wake up pattern (Wup) on the K-line. The pattern begins after the idle time on K-line with a low time of Tinil. The tester transmits the first bit of the StartCommunication Service after a time of Twup following the first falling edge. U.K.

CPR_017 The timing values for the fast initialisation and communications in general are detailed in the tables below. There are different possibilities for the idle time: U.K.

• First transmission after power on, Tidle = 300 ms.

• After completion of a StopCommunication Service, Tidle = P3 min.

• After stopping communication by time-out P3 max, Tidle = 0.

Table 3
Timing values for fast initialisation
Parameter		min value	max value
Tinil	25 ± 1 ms	24 ms	26 ms
Twup	50 ± 1 ms	49 ms	51 ms

Table 4
Communication timing values
Timing Parameter	Parameter Description	lower limit values [ms]	upper limit values [ms]
		min.	max.
P1	Inter byte time for VU response	0	20
P2	Time between tester request and VU response or two VU responses	25	250
P3	Time between end of VU responses and start of new tester request	55	5 000
P4	Inter byte time for tester request	5	20

CPR_018 The message format for fast initialisation is detailed in the following tables. (NOTE: Hex means hexadecimal) U.K.

Table 5
StartCommunication Request Message
Byte #	Parameter Name	Hex Value	Mnemonic
#1	Format byte — physical addressing	81	FMT
#2	Target address byte	EE	TGT
#3	Source address byte	tt	SRC
#4	StartCommunication Request Service Id	81	SCR
#5	Checksum	00-FF	CS

Table 6
StartCommunication Positive Response Message
Byte #	Parameter Name	Hex Value	Mnemonic
#1	Format byte — physical addressing	80	FMT
#2	Target address byte	tt	TGT
#3	Source address byte	EE	SRC
#4	Additional length byte	03	LEN
#5	StartCommunication Positive Response Service Id	C1	SCRPR
#6	Key byte 1	EA	KB1
#7	Key byte 2	8F	KB2
#8	Checksum	00-FF	CS

CPR_019 There is no negative response to the StartCommunication Request message, if there is no positive response message to be transmitted then the VU is not initialised, nothing is transmitted and it remains in its normal operation. U.K.

4.2. StopCommunication Service U.K.

4.2.1 Message description U.K.

The purpose of this communication layer service is to terminate a communication session.

CPR_020 Upon receiving a StopCommunication indication primitive, the VU shall check if the current conditions allow to terminate this communication. In this case the VU shall perform all actions necessary to terminate this communication. U.K.

CPR_021 If it is possible to terminate the communication, the VU shall issue a StopCommunication response primitive with the Positive Response parameters selected, before the communication is terminated. U.K.

CPR_022 If the communication cannot be terminated by any reason, the VU shall issue a StopCommunication response primitive with the Negative Response parameter selected. U.K.

CPR_023 If time-out of P3 max is detected by the VU, the communication shall be terminated without any response primitive being issued. U.K.

4.2.2 Message format U.K.

CPR_024 The message formats for the StopCommunication primitives are detailed in the following tables. U.K.

Table 7
StopCommunication Request Message
Byte #	Parameter Name	Hex Value	Mnemonic
#1	Format byte — physical addressing	80	FMT
#2	Target address byte	EE	TGT
#3	Source address byte	tt	SRC
#4	Additional length byte	01	LEN
#5	StopCommunication Request Service Id	82	SPR
#6	Checksum	00-FF	CS

Table 8
StopCommunication Positive Response Message
Byte #	Parameter Name	Hex Value	Mnemonic
#1	Format byte — physical addressing	80	FMT
#2	Target address byte	tt	TGT
#3	Source address byte	EE	SRC
#4	Additional length byte	01	LEN
#5	StopCommunication Positive Response Service Id	C2	SPRPR
#6	Checksum	00-FF	CS

Table 9
StopCommunication Negative Response Message
Byte #	Parameter Name	Hex Value	Mnemonic
#1	Format byte — physical addressing	80	FMT
#2	Target address byte	tt	TGT
#3	Source address byte	EE	SRC
#4	Additional length byte	03	LEN
#5	negative Response Service Id	7F	NR
#6	StopCommunication Request Service Identification	82	SPR
#7	responseCode = generalReject	10	RC_GR
#8	Checksum	00-FF	CS

4.2.3 Parameter Definition U.K.

This service does not require any parameter definition.

4.3. TesterPresent Service U.K.

4.3.1 Message description U.K.

The TesterPresent service is used by the tester to indicate to the server that it is still present, in order to prevent the server from automatically returning to normal operation and possibly stopping the communication. This service, sent periodically, keeps the diagnostic session/communication active by resetting the P3 timer each time a request for this service is received.

4.3.2 Message format U.K.

CPR_079 The message formats for the TesterPresent primitives are detailed in the following tables. U.K.

Table 10
TesterPresent Request Message
Byte #	Parameter Name		Hex Value	Mnemonic
#1	Format byte — physical addressing		80	FMT
#2	Target address byte		EE	TGT
#3	Source address byte		tt	SRC
#4	Additional length byte		02	LEN
#5	TesterPresent Request Service Id		3E	TP
#6	Sub Function = responseRequired =	[ yes	01	RESPREQ_Y
		no ]	02	RESPREQ_NO
#7	Checksum		00-FF	CS

CPR_080 If the responseRequired parameter is set to ‘yes’, then the server shall respond with the following positive response message. If set to ‘no’, then no response is sent by the server. U.K.

Table 11
TesterPresent Positive Response Message
Byte #	Parameter Name	Hex Value	Mnemonic
#1	Format byte — physical addressing	80	FMT
#2	Target address byte	tt	TGT
#3	Source address byte	EE	SRC
#4	Additional length byte	01	LEN
#5	TesterPresent Positive Response Service Id	7E	TPPR
#6	Checksum	00-FF	CS

CPR_081 The service shall support the following negative responses codes: U.K.

Table 12
TesterPresent Negative Response Message
Byte #	Parameter Name		Hex Value	Mnemonic
#1	Format byte — physical addressing		80	FMT
#2	Target address byte		tt	TGT
#3	Source address byte		EE	SRC
#4	Additional length byte		03	LEN
#5	negative Response Service Id		7F	NR
#6	TesterPresent Request Service Identification		3E	TP
#7	responseCode =	[SubFunctionNotSupported-InvalidFormat	12	RC_SFNS_IF
		incorrectMessageLength]	13	RC_IML
#8	Checksum		00-FF	CS