Technical data

Table Of Contents
Communication SFCs for Non-Configured S7 Connections
System Software for S7-300/400 System and Standard Functions - Volume 2/2
A5E00739858-01
22-9
Parameter Declaration Data Type Memory Area Description
RD OUTPUT ANY I, Q, M, D Reference to the received data area. The
following data types are allowed: BOOL,
BYTE, CHAR, WORD, INT, DWORD, DINT,
REAL, DATE, TOD, TIME,S5_TIME,
DATE_AND_TIME
and arrays of these data types except for
BOOL.
If you want to discard the oldest block of
data in the queue, assign the value NIL to
RD.
The maximum length of the receive area is
76 bytes
Indicating Reception of Data with EN_DT=0
As soon as data from a communication partner arrive, they are entered in the
queue by the operating system in the order in which they are received.
If you want to check whether at least one block of data is in the queue, call SFC 66
with EN_DT=0 and evaluate the output parameter NDA as follows:
NDA=0 means that the queue does not contain a block of data. REQ_ID is
irrelevant, RET_VAL has the value W#16#7000.
NDA=1 means that there is at least one block of data in the queue that can be
fetched.
In this case, you should also evaluate the output parameter RET_VAL and, if
applicable, REQ_ID. RET_VAL contains the length of the block of data in
bytes, REQ_ID contains the job identifier of the sending block. If there are
several blocks of data in the queue, REQ_ID and RET_VAL belong to the
oldest block of data in the queue.
Data receiv ed t2
Receive resource s
Data receiv ed t1
t1 t2
t
Queue
REQ_ID
RD
EN_DT
"X_RCV"
N
DA
0
Querying Data Reception
Data receipt