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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