Siemens SIMATIC S5 CP 523 Manual page 194

Using the "SEND" and "Receive" Function Blocks
8.1.3 Structure of the Status Byte
The status bytes of "SEND" FB 200 and "RECEIVE" FB 201 are identical. The status byte gives
information on 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 can not be
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 too
small for
Receive data
Error flagged in
the CBS
8-4
Bit 7 Bit 6 Bit 5
0 0 1
0 1 0
0 1 0
1 0 0
Figure 8-1. 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