Schneider Electric Altivar 212 Modbus functions available, Read one word, Function 3, quantity =

Modbus services

Modbus functions available

The following table indicates which Modbus functions are managed by the Altivar 212 and specifies their limits. The "read" and "write" functions are defined from the point of view of the master.

Code

Function name

Size of data

Altivar 212 function name

Broadcast

3 = 16#03	Read Holding Registers	1 object	Read one word	Yes
		1 ... 5 objects	Read indirect block	Yes
6 = 16#06	Write Single Register	1 objects		Yes
16 = 16#10	Write Multiple Registers	1 object	Write one word	Yes
		2 objects	Write indirect block	Yes
43/14 = 16#2B/0E	Read Device Identification	3 objects		No

Read one word (03)

Function 3, quantity = 1

One word function permits to read one parameter value. All parameter of the Altivar 212 can be read. Request:

Slave no.	Function code	Starting address			Quantity of registers				CRC16
						(fixed)
	03	Hi		Lo	00		01	Lo		Hi
1 byte	1 byte		2 bytes			2 bytes			2 bytes

Response:

Slave no.	Function code	Byte count	Register value				CRC16
	03		Hi		Lo	Lo		Hi
1 byte	1 byte	1 byte		2 bytes			2 bytes

Error response:

Slave no.	Function code	Exception		CRC16
	83	code	Lo		Hi
1 byte	1 byte	1 byte	1 byte		1 byte

Example: Read [Output frequency] (Fd00) on Altivar 212 at slave address 1

Request:

01 03 FD 00 00 01 B5 A6

Response:

01 03 02 17 70 B6 50

Example: Invalid read of 2 words

Request:

01 03 FD 00 00 02 F5 A7

Error response:

01

83

03

01 31

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