Siemens SIMATIC S5-100U System Manual page 348

Connecting the S5-100U to SINEC L1
Structure of the Coordination Byte Receive (KBE)
Figure 13-7 shows the structure for receiving data (KBE).
Bit 7 6 5
Figure 13-7. Structure of the Coordination Byte Receive (KBE)
Structure of the Control Program for Receiving Data:
1. Check bit 7 of the KBE to see if it is possible to read the data from the Receive Mailbox. Bit 7
must be set to "0" so that the Receive Mailbox can be read.
2. In addition, you can scan through the KBE for the following errors and operating conditions:
- At least one slave has failed.
- The bus is in RUN (STOP) mode.
- The received data pack comes as an express transmission.
Special Features
If you have reserved too little memory for the Receive Mailbox, the available memory area is filled
up completely (flag area FY0 to FY255, DW0 to DW255). Therefore, the remaining receive data
cannot be stored. In this case, the programmable controller does not generate an overflow
message.
You can find sample programs for sending and receiving data in the SINEC L1 manual (in the
chapter on "Programming").
13-10
KBE
4 3 2 1 0
0: No error
1: Error during last data transfer
0: No slave failed
1: At least one slave failed
0: Bus in STOP mode
1: Bus in RUN mode
0: No message
1: Data arrives as express transmission
0: Program can access the Receive
Mailbox
(operating system can not access)
1: Operating system accepts data into the
Receive Mailbox
(program can not access)
EWA 4NEB 812 6120-02b
S5-100U