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 |
Received 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 |
