Schneider Electric VW3 A3 303 user manual Read non-existent or protected parameters

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8. Modbus protocol

8. 13. Read non-existent or protected parameters

If a set of parameters is read using a Modbus function, the value returned for non-existent and protected parameters is equal to 16#8000.

If the same Modbus function is used to read parameters, all of which are non-existent or protected, the drive sends back an exception response with an error code equal to 2.

Example of non-existent or protected parameters being read:

In this example, the same request to read a non-existent parameter followed by 2 existing parameters is used several times in a row in order to demonstrate the effects of parameter protection.

The "Read Holding Registers" request (3) is addressed to a drive with a Modbus address of 12 (16#0C). The read operation is performed for 3 consecutive words, starting with address 8400.

Logic address

Parameter

Value

8400 = 16#20FA

Non-existent

-

8401 = 16#20D1

[Profile] (CHCF)

3

 

 

 

8402 = 16#20D2

[Copy channel 1 ↔ 2] (COP)

2

Request:

Slave no.

Request code

No. of 1st word

No. of words

 

CRC16

 

 

Hi

 

Lo

Hi

 

Lo

Lo

 

Hi

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0C

03

20

 

D0

00

 

03

0E

 

EF

 

 

 

 

 

 

 

 

 

 

 

Response:

Scenario no. 1: Parameters CHCF (8401) and COP (8402) not protected V Successful reading of these two parameters and value equal to 16#8000 for the non-existent parameter located at address 8400.

Slave no.

Response code

No. of bytes read

Value 8400

Value 8401

Value 8402

CRC16

 

 

 

Hi

 

Lo

Hi

 

Lo

Hi

 

Lo

Lo

 

Hi

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0C

03

06

80

 

00

00

 

03

00

 

02

17

 

E4

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Scenario no. 2: Parameter CHCF (8401) protected and COP (8402) not protected V Successful reading of COP and value equal to 16#8000 for the non-existent parameter located at address 8400 and for parameter CHCF.

Slave no.

Response code

No. of bytes read

Value 8400

Value 8401

Value 8402

CRC16

 

 

 

Hi

 

Lo

Hi

 

Lo

Hi

 

Lo

Lo

 

Hi

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0C

03

06

80

 

00

80

 

00

00

 

02

CE

 

24

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Scenario no. 3: Parameters CHCF (8401) and COP (8402) protected V Exception response (response code = 16#80 + request code), as all the parameters read are either non-existent, or protected; error code equal to 2 (the word addresses indicated in the request do not exist in the slave).

Slave no.

Response code

Error code

CRC16

 

 

 

Lo

 

Hi

 

 

 

 

 

 

 

 

 

 

0C

80+03 = 83

02

51

 

32

 

 

 

 

 

 

38

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Contents Altivar Contents Before you begin Electric shock will result in death or serious injuryProgramming Manual Installation ManualDocumentation structure Communication Parameters ManualNotation IntroductionPresentation Receipt Hardware setupInstalling the card in the drive Hardware descriptionCoding the address Switch codingChoosing polarization Address 1234Modbus RS485 standard Connecting to the busWiring recommendations Connection cables Connection via RJ45 wiring systemConnection accessories TWD XCA RJ030 Connection cables for the masterType of master Master interface Description Catalog number TSX SCP CMRS485 double shielded twisted pair Connection via junction boxesDescription Catalog Number Subscriber socket CablesTSX CSA500 TSX P ACCConfiguration Communication parametersControl via Modbus or the terminals in I/O profile Control CommandControl via Modbus in I/O profile Parameter Value CommentControl via Modbus in Drivecom profile Control via Modbus or the terminals in Drivecom profileConfiguration RDY NET Example of configuration via the graphic display terminalCommunication scanner COM. Scanner InputCommunication faults COM. Fault ManagementFormat CONFIG. COMM. MAPMonitored parameters Format Range Terminal displayLEDs DiagnosticsChecking the address Green RUN Red ERR Meaning Corrective actionCOM. Scanner Input MAP RUN NETCommunication MAP COM Scan Output MAP CMD. Word ImageCOM Scan Output MAP Input variable Scanner parameterOutput variable Scanner parameter Communication fault Card faultSlave Slave j Slave k Modbus protocolPrinciple Modes RTU modeAscii mode Slave address Function code DataCode Modbus name Description Broadcast Size of data Modbus functions availableRead Holding/Input Registers 3/4 Write Single Register Diagnostics Get Comm Event Counter 11 = 16#0B Write Multiple Registers 16 = 16#10Read/Write Multiple Registers 23 = 16#17 Read Device Identification 43 = 16#2B MachineExample of positive response MEICode Modbus name Description Size of data Output variables Logic address Default assignmentInput variables Logic address Default assignment Parameter Logic Input variable address Logic address Default valueParameter Logic Read Input monitoring Output controlParameter assigned Value Parameter assignedResponse Code Error codeException responses Read non-existent or protected parameters Logic address Parameter ValueAppendix RS485 standardModbus 2-wire standard schematic MasterModbus 4-wire standard schematic Uni-Telway schematic Wire Jbus schematic Type of trunk cable Cable with 1 shielded twisted pairRecommendations Creating a Modbus bus using non-standard equipmentDifferent scenarios Calculating the polarization ExampleContact no. Signal RS485 schematic for the cardCard connector pinout SUB-DAtv71ModbusJbusENV1 2005-05
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