PRVREC (FB)

FUNCTION_BLOCK PRVREC

A Field Device can receive a request to provide a process data record to a Host Controller or Supervisor. The host may use the RDREC function block.

The application program is informed about this request and can provide the requested process data record using the PRVREC function block.

This function blocks contains the methods to check, receive and respond a request for a process data record.

All aspects of providing a process data record may use one function block instance, the different methods are distinguished using the MODE input.

If a data record is received (with MODE=1 or MODE=2), the NEW output indicates that the data record is stored in the variable given at the RECORD parameter.

If the function block refuses to accept the data record, the CODE1 input sets the Error Code1, and the CODE2 input sets the Error Code 2 of the negative response.

If an error occurred, the ENO=0 indicates an error and the STATUS output contains the error code.// | If an error occurred, the ENO=0 indicates an error and the STATUS output contains the error code.

Note

The application program of the Field Device shall acknowledge the received request, otherwise the Host Controller will get a timeout error or the device stack will send a negative response.

Code-Example

PROGRAM ProvideData
VAR
    prvData : CommFB.PRVREC;
    data : ARRAY[0..3] OF BYTE := [0,1,2,3];        // some dummy data
END_VAR

// Variant 1: receive data for a specific slot:
prvData.EN := 1;
prvData.F_ID := CommFB.SUBSLOT_ID(EN := TRUE, PN_Device.DeviceID, 2, 1);    // get ID of Slot 2 of the specified device
prvData(MODE := CommFB.PRVREC_MODE.RECEIVE_BY_SLOT);        // get request
IF prvData.NEW THEN     // process record
    IF(prvData.SLOT = 1 AND  prvData.INDEX = 2) THEN
        prvData(MODE := 3, LEN:=4, RECORD := ADR(data));    // pos. response with data
    END_IF
END_IF

// Variant 2: check for request, then decide to process it (receive + pos./neg. response)
prvData(MODE := CommFB.PRVREC_MODE.CHECK, F_ID := PN_Device.DeviceID);  // get request
IF(prvData.NEW) THEN
    // Reject everything else.
    // If a request from the host is not confimed by the aplication, the stack may send a neg. response after a timeout.
    prvData(MODE := 4, CODE1 := 16#B2);
END_IF

InOut:

Scope	Name	Type	Comment
Input	EN	BOOL	Enable
	MODE	UINT	Function specifier, see PRVREC_MODE
	F_ID	DWORD	Slot / subslot to filter the data records to receive
	CODE1	BYTE	Reason for negative response. (see ErrorCode1_RW)
	CODE2	BYTE	Reason for negative response. (0 or user specific)
	LEN	UINT	Length of a data record to provide
	RECORD	POINTER TO BYTE	Provided data record
Output	ENO	BOOL	Function enabled
	NEW	BOOL	New data record requested
	STATUS	DWORD	Field Device interface status
	SLOT	UINT	Slot the record is requested for
	SUBSLOT	UINT	Subslot the record is requested for
	INDEX	UINT	Index of the requested data record
	RLEN	UINT	Length of the requested data record