Council Regulation (EEC) No 3821/85Show full title

[F1 [F2 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.

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.

[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.

[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 re-initialised.

[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.

[CPR_010] The StartCommunication Request message must be physically addressed.

[CPR_011] Initialising the VU for services is performed through a ‘ fast initialisation ’ method,

• 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,

• 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.

[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.

[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:

• first transmission after power on, T _idle = 300 ms.

• after completion of a StopCommunication Service, T _idle = P3 min.

• [X1 After stopping communication by time-out P3 max, T _idle = 0.]

Editorial Information

X1 Substituted by Corrigendum to Commission Regulation (EC) No 1360/2002 of 13 June 2002 adapting for the seventh time to technical progress Council Regulation (EEC) No 3821/85 on recording equipment in road transport (Official Journal of the European Communities L 207 of 5 August 2002).

Table 3

Timing values for fast initialisation

Parameter		minimum value	maximum 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)
		minimum	maximum
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:

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	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.

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.

[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.

[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.

[CPR_023] If time -out of P3max is detected by the VU, the communication shall be terminated without any response primitive being issued.

4.2.2. Message format U.K.

[CPR_024] The message formats for the StopCommunication primitives are detailed in the following tables:

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	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.

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 no]	01 02	RESPREQ_Y 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.

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:

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 incorrectMessageLength]	12 13	RC_SFNS_IF RC_IML
#8	Checksum	00-FF	CS] ]

Textual Amendments

F1 Inserted by Council Regulation (EC) No 2135/98 of 24 September 1998 amending Regulation (EEC) No 3821/85 on recording equipment in road transport and Directive 88/599/EEC concerning the application of Regulations (EEC) No 3820/85 and (EEC) No 3821/85.

F2 Substituted by Commission Regulation (EC) No 1360/2002 of 13 June 2002 adapting for the seventh time to technical progress Council Regulation (EEC) No 3821/85 on recording equipment in road transport (Text with EEA relevance).