FUNCTION_BLOCK RCVREC
A Field Device can receive an acyclic process data record from a Host Controller or a Supervisor (The Host may use the WRREC function block).
The application of a programmable field device is informed about this request and can receive the data using the RCVREC function block.
This function blocks contains the methods to check, receive and acknowledge a process data record.
All aspects of receiving 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 Code 1, 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.
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 ReceiveData
VAR
recvData: CommFB.RCVREC;
data : ARRAY [0..64] OF BYTE;
recvAll: CommFB.RCVREC;
param1 : ARRAY [0..7] OF BYTE;
param2 : ARRAY [0..7] OF BYTE;
END_VAR
// Variant 1: receive data for a specific slot:
recvData.EN := 1;
recvData.F_ID := CommFB.SUBSLOT_ID(EN := TRUE, PN_Device.DeviceID, 2, 1); // get ID of Slot 2 of the specified device
recvData.MLEN := SIZEOF(data);
recvData.RECORD := ADR(data);
recvData (MODE := CommFB.RCVREC_MODE.RECEIVE_BY_SLOT); // receive data and write it to RECORD
IF recvData.NEW THEN
IF(recvData.INDEX = 10) THEN
// ...process and opt. check received data
recvData(MODE := CommFB.RCVREC_MODE.POS_RESPONSE); // send pos. response to host
ELSE
recvData(MODE := CommFB.RCVREC_MODE.NEG_RESPONSE, CODE1 := CommFB.ErrorCode1_RW.Invalid_index); // signal error to host
END_IF
END_IF
// Variant 2: check for any request and then (opt.) receive it in a second step
// MODE := 0 = CommFB.RCVREC_MODE.CHECK
// MODE := 1 = CommFB.RCVREC_MODE.RECEIVE
// MODE := 3 = CommFB.RCVREC_MODE.POS_RESPONSE
// MODE := 4 = CommFB.RCVREC_MODE.NEG_RESPONSE
recvAll(EN := TRUE, MODE := 0); // check for new data
IF(recvAll.NEW) THEN // received data
IF(recvAll.SLOT = 1 AND recvAll.INDEX = 100) THEN
recvAll(MODE := 1, MLEN := SIZEOF(param1), RECORD := ADR(param1)); // get data
recvAll(MODE := 3); // pos. response
ELSIF(recvAll.SLOT = 3 AND recvAll.INDEX = 200) THEN
recvAll(MODE := 1, MLEN := SIZEOF(param2), RECORD := ADR(param2)); // get data
recvAll(MODE := 3); // pos. response
ELSE
recvAll(MODE := 4, CODE1 := CommFB.ErrorCode1_RW.Invalid_slot_or_subslot); // signal error to host
END_IF
END_IF
InOut:
|
Scope |
Name |
Type |
Comment |
|
Input |
EN |
BOOL |
The function is invoked by EN=1. |
|
MODE |
UINT |
Function specifier, see RCVREC_MODE |
|
|
F_ID |
DWORD |
Slot / subslot to filter the data records to receive |
|
|
MLEN |
UINT |
Maximum length of a data record to receive |
|
|
CODE1 |
BYTE |
Reason for negative response. (see ErrorCode1_RW) |
|
|
CODE2 |
BYTE |
Reason for negative response. (0 or user specific) |
|
|
RECORD |
POINTER TO BYTE |
Received data record. Shall be at least of MLEN byte |
|
|
Output |
ENO |
BOOL |
Function enabled |
|
NEW |
BOOL |
New data record received |
|
|
STATUS |
DWORD |
Field Device interface status |
|
|
SLOT |
UINT |
Slot the record is received for |
|
|
SUBSLOT |
UINT |
Subslot the record is received for |
|
|
INDEX |
UINT |
Index of the received data record |
|
|
LEN |
UINT |
Length of the received data record |
