eipReadAttr

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Function Block - Sends an explicit message (UCMM) to an EtherNet/IP adapter to read a single CIP attribute.

Inputs

Input	Data Type	Range	Unit	Default	Description
Attr	UINT				Identifier of the CIP attribute.
Class	UINT				Class identifier of the CIP object.
Data	UINT[ ]				Buffer where to store the received data. If the actual attribute length is greater than the size of this array, the value is truncated when read.
Inst	UINT				Instance identifier of the CIP object.
SrvIP	STRING				IP address of the server (adapter) (e.g., configured in the EtherNet/IP Scanner configuration).
Snd	BOOL	FALSE, TRUE	N/A	No default	A rising edge on this input starts the exchange. The DONE output signals the end of exchange.

Outputs

Output	Data Type	Range	Unit	Description
Done	BOOL	FALSE, TRUE	N/A	This output is TRUE during one cycle when the exchange is finished, whether the exchange succeeded or failed. Warning: This output can be TRUE just after the call to block when starting a new exchange in case of invalid parameters.
EmErr	UINT			In case of a UCMM error, this is the CIP general status error code.
EmErrExt	UINT			In case of a UCMM error, this is the CIP extended status error code.
Err	UINT			Main error report. Can be one of these values: 0 = No error. 1 = Invalid input arguments. 2 = System is busy (see remarks). 3 = Timeout waiting for the answer (the timeout value is 3 seconds). 4 = UCMM error was returned by the server others = internal errors (reserved for technical support).
RcvSize	UINT			Actual size of the CIP attribute answered by the server. If this size is greater than the size of the DATA input array, it indicates the value was truncated.

Remarks

The CIP instance number can be 16-bits [1...65535].
The servers (adapters) accessed by this block must be configured in the EtherNet/IP Scanner fieldbus configuration.
Only one explicit message (read or write) can be sent at one time to the same server.
- If another message is pending you receive the error report 3 (busy) after calling the block to start a new exchange.
Consider SerializeIn and SerializeOut functions for extracting data from the read buffer.

FBD Language Example

Not available.

FFLD Language Example

Not available.

IL Language Example

Not available.

ST Language Example

// used variables
// Inst_eipReadAttr : eipReadAttr ;
// bRead : BOOL ; (* request for READ *)
// DataRead : ARRAY [0 .. 15] OF USINT ; (* read data *)
// Server identification and CIP things
#define SRVIP '192.168.33.21'
#define CLASSID UINT#100
#define INSTID_READ UINT#1
#define ATTRID UINT#3
/////////////////////////////////////////////////////////////////////////////////////////
// requested READ command
if bRead then
    Inst_eipReadAttr (bRead, SRVIP, CLASSID, INSTID_READ, ATTRID, DataRead);
end_if;
// READ answer here ?
if Inst_eipReadAttr.Done then
// check answer - if OK answered data is in DataRead array
    if Inst_eipReadAttr.Err = 0 then
        printf ('READ ok - size = %lu bytes',
            any_to_dint (Inst_eipReadAttr.RcvSize));
    else
        printf ('READ Error %lu (UCMM Error %lu, %lu)',
            any_to_dint (Inst_eipReadAttr.Err),
            any_to_dint (Inst_eipReadAttr.EmErr),
            any_to_dint (Inst_eipReadAttr.EmErrExt));
    end_if;
// reset READ command and block input
    Inst_eipReadAttr (false, SRVIP, CLASSID, INSTID_READ, ATTRID, DataRead);
    bRead := false;
end_if;