Siemens SIMATIC S5 CP 523 Manual page 212

Using the "SEND" and "RECEIVE" Function Blocks
8.2.2 Structure of the Status Byte
The status bytes for "SEND" FB 200 and "RECEIVE" FB 201 are identical. The status byte contains
information about whether:
• Receive data is available (bit 0 = 1)
• The Send mailbox is empty (bit 1 = 1)
If the Send mailbox is occupied, the Send job initiated by calling "SEND" FB 200 is not
executed.
• Errors have occurred (bit 3 = 1)
If bit 3 is set, bits 4 to 7 contain the error code.
SEND FB
Parameter error
RECEIVE FB
Parameter error
Target DB for
receive data too
small
Error flagged
in CBR
8.2.3 Schematic Representation of the Method of Operation of "RECEIVE"
FB 201
Note:
This section is intended merely to explain how "RECEIVE" FB 201 works. You do not require this
information to use "RECEIVE" FB 201.
8-22
Bit 7 Bit 6 Bit 5
0 0 1
0 1 0
0 1 0
1 0 0
Figure 8-3. Structure of the "STAT" Status Byte
Status byte
Bit 4 Bit 3 Bit 2
1
0
1
0
Bit 1 Bit 0
1 Receive data
available
0 No receive data
available
1 Permission to send
0 No permission to send
1 Bits 4 to 7 contain
error code
0 No errors
EWA 4NEB 811 6044-02a
CP 523