Schneider Electric VW3 A3 303 Modbus functions available, Read Holding/Input Registers 3/4

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8. Modbus protocol

8. 3. Modbus functions available

The following table indicates which Modbus functions are managed by the Altivar 71 and specifies their limits. The "read" and "write" functions are defined from the point of view of the master.

Code	Modbus name	Description	Broadcast	Size of data
3 = 16#03	Read Holding Registers	Read N output words	NO	63 words, max.

4 = 16#04	Read Input Registers	Read N input words	NO	63 words, max.

6 = 16#06	Write Single Register	Write one output word	YES

8 = 16#08	Diagnostics	Diagnostics	NO

11 = 16#0B	Get Comm Event Counter	Read counter	NO

16 = 16#10	Write Multiple Registers	Write N output words	YES	61 words, max.

23 = 16#17	Read/Write Multiple Registers	Read/write N words	NO	20/20 words max.

43 = 16#2B	Read Device Identification	Identification	NO

8. 4. Read Holding/Input Registers (3/4)

Functions 3 and 4 access all the drive registers that make no distinction between the "Holding" or "Input" types.

Request:

Slave no.

03/04

No. of first word

Number of words

CRC16

Hi

Lo

Hi

Lo

Lo

Hi

1 byte

1 byte

2 bytes

2 bytes

2 bytes

Response:

Slave no.

03/04

Number of

First word value

-------

Last word value

CRC16

bytes read

Hi

Lo

Hi

Lo

Lo

Hi

1 byte

1 byte

1 byte

2 bytes

2 bytes

2 bytes

Example: Use function 3 to read 4 logic address words 3102 to 3105 (16#0C1E to 16#0C21) on slave 2, where:

•SFr = Switching frequency = 4 kHz (logic address 3102 = 16#0028)

•tFr = Maximum output frequency = 60 Hz (logic address 3103 = 16#0258)

•HSP = High speed = 50 Hz (logic address 3104 = 16#01F4)

•LSP = Low speed = 0 Hz (logic address 3105 = 16#0000)

Request:

02

03

0C1E

0004

276C

Response:

02	03	08	0028	0258	01F4	0000	52B0

	Value of:		3102	3103	3104	3105
Parameter code:			SFr	tFr	HSP	LSP

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Contents Altivar Contents Electric shock will result in death or serious injury Before you beginCommunication Parameters Manual Installation ManualDocumentation structure Programming ManualIntroduction PresentationNotation Hardware description Hardware setupInstalling the card in the drive ReceiptSwitch coding Choosing polarizationCoding the address 1234 AddressConnecting to the bus Wiring recommendationsModbus RS485 standard Connection via RJ45 wiring system Connection accessoriesConnection cables TSX SCP CM Connection cables for the masterType of master Master interface Description Catalog number TWD XCA RJ030Cables Connection via junction boxesDescription Catalog Number Subscriber socket RS485 double shielded twisted pairTSX P ACC TSX CSA500Communication parameters ConfigurationParameter Value Comment Control CommandControl via Modbus in I/O profile Control via Modbus or the terminals in I/O profileControl via Modbus or the terminals in Drivecom profile Control via Modbus in Drivecom profileConfiguration COM. Scanner Input Example of configuration via the graphic display terminalCommunication scanner RDY NETCOM. Fault Management Communication faultsFormat Range Terminal display CONFIG. COMM. MAPMonitored parameters FormatGreen RUN Red ERR Meaning Corrective action DiagnosticsChecking the address LEDsCOM Scan Output MAP CMD. Word Image RUN NETCommunication MAP COM. Scanner Input MAPInput variable Scanner parameter Output variable Scanner parameterCOM Scan Output MAP Card fault Communication faultModbus protocol PrincipleSlave Slave j Slave k Slave address Function code Data RTU modeAscii mode ModesModbus functions available Read Holding/Input Registers 3/4Code Modbus name Description Broadcast Size of data Write Single Register Diagnostics Write Multiple Registers 16 = 16#10 Get Comm Event Counter 11 = 16#0BRead/Write Multiple Registers 23 = 16#17 Machine Read Device Identification 43 = 16#2BMEI Example of positive responseOutput variables Logic address Default assignment Input variables Logic address Default assignmentCode Modbus name Description Size of data Input variable address Logic address Default value Parameter Logic ReadParameter Logic Value Parameter assigned Output controlParameter assigned Input monitoringCode Error code Exception responsesResponse Logic address Parameter Value Read non-existent or protected parametersRS485 standard AppendixMaster Modbus 2-wire standard schematicModbus 4-wire standard schematic Uni-Telway schematic Type of trunk cable Cable with 1 shielded twisted pair Wire Jbus schematicCreating a Modbus bus using non-standard equipment Different scenariosRecommendations Example Calculating the polarizationSUB-D RS485 schematic for the cardCard connector pinout Contact no. SignalAtv71ModbusJbusENV1 2005-05