LIAN 98(en) : Protocol ABB RP 570/ RP 571, Telegram structure

ABB RP 570/ 571 : Telegram structure

Transmission of a single telegram byte

The smallest unit of information within the protocol is a byte. Each transmission byte is composed of - 1 start bit, 8 data bits, 1 parity bit and 1 stop bit. The parity bit supplements the byte to even parity. Within the data bits the least significant bit is sent first. ( LSB first ).

logical 0 : + 12 Volt / logical 1 : - 12 Volt

Telegram format with variable length

The length of the information within the message is variable. In addition to this information block of variable length, the message has also a header and address block of fixed length.

The telegram with variable length is used for data transmission of user data between master station and slave station and in the opposite direction.

Data telegram RP 570/ 571 :

Telegram format with fixed length

Telegrams with a fixed length are 5 bytes long and are recognizable by the start character 10H.

RTU number

A substation, which is the recipient of a message in control direction, is addressed by the RTU number or is identified as the sender of the message in monitoring direction. The RTU number is in the range of 1... 255. The number NULL is only used, if the master wants to send commands simultaneously to all substations. These commands are not acknowledged by the receivers. Only certain messages may be sent with the "broadcast address = 0".

CMD bit ( command/ direction bit )

CMD = 1 : Telegram from the master to the substation.
CMD = 0 : Telegram from the substation to the master.

Function field

The function field uniquely identifies the message and is different in control and monitoring direction.

Control direction

Monitoring direction

M / D

M/D = 1 corresponds to the dialogue mode, i.e. The recipient must acknowledge the order.
M/D = 0 corresponds to the monologue mode, i.e. the master does not expect an acknowledge.

Normally, all telegrams addressed to a recipient are sent in dialogue mode. However, exceptions are allowed, e.g. Positioning and control commands. All broadcast messages are sent in monologue mode.

SEQ ( sequence number )

The sequence number is a counter ( 0... 3 ) for all dialogue mode messages in control direction, which is always increased by one after sending a telegram. It is used for the message repetition in communication disorders. Telegrams in monologue mode do not change the sequence number.

Function code

The function code in the function field identifies the message type.

Commands in control direction

Function code		Start byte
0	Request A Query for data of priority 1. Response is made with CCR1 when no data available. It is only used under certain conditions in party line mode.	10H	RA
1	Setpoint Message A distiction is made between the following command formats: - Analogical Setpoint Message ( -2048.. +2047 ) - Digital Setpoint Message ( 15 bit transparent ) Response is made with EXR or NXR as acknowledge to the request.	68H	SPM
2	Function Table Project data can be transmitted from the master to the slave with the help of the parameter data set. For each data point ( command, message, measurand, ... ) is at least one FTAB command required. Further commands may follow for the complete parameterization. Response is made with EXR or NXR as acknowlege to the request.	68H	FTAB
3	Inhibit Command The inhibit command cancels a previously done selection with the select command. Response is made with EXR or NXR as acknowledge to the request.	68H	IHC
4	Request X	68H	RX
5	Check Back before Execute The select command selects in the substation the object to be switched. This object is switched with a final execute command ( EXC ). Response is made with CBR or NXR as acknowlege to the request.	68H	CBXC
6	Function Command With this command the master can initiate actions in the substation. The mode of the action or reaction is given by the data fields. Response is made with EXR or NXR as acknowlege to the request.	68H	FCOM
7	Reset Sequence Number Is used for the synchronization of the sequence number ( SEQ-number ) between the master and the lower level. Response is made with EXR or NXR as acknowlege to the request.	10H	RSEQ
8	Request B The normal command to query data. Response is made with CCR2 when no data available.	10H	RB
9	Immediate Execute Command This command is used for the execution of an one level impulse command. Commands are generally double commands whereat the output time is set for each command object via the parameter data set. Response is made with EXR or NXR as acknowlege to the request.	68H	IXC
10	Function code is not used !
11	General Output Message The text command is available in four versions : - binary text command; ( 1 bit ) - binary text command; ( 2 bit ) - binary text command; ( 16 bit transparent ) - analogue text command; ( -2048.. +2047 ) Response is made with EXR or NXR as acknowlege to the request.	68H	GOM
12	Time Sync Instruction With the Time Sync Instruction date and time for the time synchronization are transmitted to the lower level. Response is made with EXR or NXR as acknowlege to the request.	68H	TSI
13	Execute Command The double-throw process command consists of a select command ( CBXC ) to select the object to be switched and an execute command. Response is made with EXR or NXR as acknowlege to the request.	68H	EXC
14	Transparent Data in Command direction Is used for file transfer and online diagnostics. Response is made with EXR or NXR as acknowlege to the request.	68H	TDC

15	Status Check Instruction ( RP 570 - General Interrogation ) The general interrogation command has several functions such as the inclusion or resumption of the communication or the interrogation of the process image at runtime. Response is made with EXRR after the restart of the substation or EXR or NXR as acknowlege to the request.	10H	SCI
15	Status Check Instruction ( RP 571 - General Interrogation )	68H	SCI

Messages in monitoring direction

Function code		Start byte
0	Cycle Complete Response, priority level 1 The message is sent as acknowlege to the request command "Request A" if there are no other data with priority 1 to transmit.	10H	CCR1
1	Cycle Complete Response, priority level 2 The message is sent as acknowlege to the request command "Request B" if there are no other data to transmit.	10H	CCR2

2	Execute Response, RTU restarted ( RP 570 ) This message is sent once after the restart as acknowledge to command "Status Check Instruction" ( SCI ).	10H	EXRR
2	Execute Response, RTU restarted ( RP 571 )	68H	EXRR

3	Executed Response ( RP 570 )	10H	EXR
3	Executed Response ( RP 571 )	68H	EXR

4	Not Executed Response ( RP 570 )	10H	NXR
4	Not Executed Response ( RP 571 )	68H	NXR

5	Terminal Status Message A Terminal Status Message is sent when at least one bit in one of the two status words ( Ident 1 or Ident 2 ) has changed. The transmission occurs on the queries "Request A" or "Request B".	68H	TSTA
6	Terminal Status Message, Satellites	68H	TSTS
7	Terminal Event Message Terminal Event Messages are spontaneous messages to the control system. Before the transmission they are entered into a queue. Within a cycle 1 the event message is created. The transmission occurs on the queries "Request A" or "Request B".	68H	TEV
8	Terminal Event Message, Satellites	68H	TEVS
9	Memory Contents Message	68H	MCM
10	Check Back Response This message is sent as positive execute acknowledge to a select command "Check Back before Execute" ( CBXC ).	68H	CBR
11	System Message System Messages include information about events and occured errors. Before sending they are listed into a queue. Within a cycle only one event message is generated. The transmission occurs only on the query "Request B".	68H	SYSM
12	Polling Request Instruction	10H	PRI
13	Acknowledge ( RP 571 )	10H	ACK
14	Transparent Data in Response direction Transparent Messages are the reaction to transparent commands ( TDC ). They are transmitted within the normal request cycle "Request B". Used for file transfer and online diagnostics.	68H	TDR
15	Negative Acknowledge ( RP 571 )	68H	NACK
16	Function code is not used !
17	Function code is not used !
18	Function code is not used !
19	Function code is not used !
20	Analog Value without Status, priority 1 Analog Values without Status are generated by spontaneous change of the measured value and by measured values to be transmitted cyclically. The transmission occurs on the queries "Request A" oder "Request B".	68H	AVM
21	Analog Value without Status, priority 2/ 3 The transmission occurs only on the query "Request B".	68H	AVM
22	Analog Value with Status, priority 1 Analog Values with Status are generated by spontaneous change of the measured value or its status, general interrogation and measured values to be transmitted cyclically. The transmission occurs on the queries "Request A" oder "Request B".	68H	AVS
23	Analog Value with Status, priority 2/ 3 The transmission occurs only on the query "Request B".	68H	AVS
24	Indication without Status, priority 1 Indications without Status are generated by spontaneous change of a message data point within a message block. A message block includes 16 single- or 8 double messages or any mixture of it. A maximum of 10 blocks can be summarized in one message. The transmission occurs on the queries "Request A" oder "Request B".	68H	IDM
25	Indication without Status, priority 2/ 3 The transmission occurs only on the query "Request B".	68H	IDM
26	Indication with Status, priority 1 Indications without Status are generated by spontaneous change of a message data point or its status or by a general interrogation. A maximum of 6 blocks can be summarized within a message. The transmission occurs on the queries "Request A" oder "Request B".	68H	IDS
27	Indication with Status, priority 2/ 3 The transmission occurs only on the query "Request B".	68H	IDS
28	Digital Value Message, priority 1 The transmission occurs on the queries "Request A" oder "Request B".	68H	DVM
29	Digital Value Message, priority 2/ 3 The transmission occurs only on the query "Request B".	68H	DVM
30	Pulse Counter Message, priority 1 The transmission occurs on the queries "Request A" oder "Request B".	68H	PCM
31	Pulse Counter Message, priority 2/ 3 The transmission occurs only on the query "Request B".	68H	PCM
32	Event Recording Message for Indications The transmission occurs only on the query "Request B".	68H	ERMI
33	Event Recording Message for Analog Measured Values The transmission occurs only on the query "Request B".	68H	ERMA
34	Event Recording Message for Digital Measured Values	68H	ERMD
35	Post Mortem Review Message, Indicating event	68H	PMRI
36	Post Morten Review Message, Values	68H	PMRV
37	Digital Value Long Message, priority 1	68H	DVL
38	Digital Value Long Message, priority 2/ 3	68H	DVL
39	Pulse Counter, priority 1	68H	PCT
40	Pulse Counter, priority 2/ 3	68H	PCT
41	Event Recording Message for Indications with Relative Time	68H	ERMIR
42	Function code is not used !
43	Event Recording Message Fault Distance	68H	ERMFD
44	Event Recording Message for Commands	68H	ERMC
45	Function code is not used !

63	Function code is not used !
64	Analog Value without Status, priority 1, CCR included	68H	AVM
65	Analog Value without Status, priority 2/ 3, CCR included	68H	AVM
66	Analog Value with Status, priority 1, CCR included	68H	AVS
67	Analog Value with Status, priority 2/ 3, CCR included	68H	AVS
68	Indication without Status, priority 1, CCR included	68H	IDM
69	Indication without Status, priority 2/ 3, CCR included	68H	IDM
70	Indication with Status, priority 1, CCR included	68H	IDS
71	Indication with Status, priority 2/ 3, CCR included	68H	IDS
72	Digital Value Message, priority 1, CCR included	68H	DVM
73	Digital Value Message, priority 2/ 3, CCR included	68H	DVM
74	Pulse Counter Message, priority 1, CCR included	68H	PCM
75	Pulse Counter Message, priority 2/ 3, CCR included	68H	PCM
76	Digital Value Long Message, priority 1, CCR included	68H	DVL
77	Digital Value Long Message, priority 2/ 3, CCR included	68H	DVL
78	Pulse Counter, priority 1, CCR included	68H	PCT
79	Pulse Counter, priority 2/ 3, CCR included	68H	PCT
80	Function code is not used !

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Manual LIAN 98