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S5-115U Manual
"Send" Coordination Byte (CBS) (Flag byte or high byte in data word)
2
7
SEND-PERM
0: The program can process the Send mailbox. The operating system has no access.
1: The operating system sends data from the Send mailbox over the LAN. The
program has no access.
indicates irrelevant bits
Figure 12-8. Structure of the "Send" Coordination Byte
The coordination bytes, the Send mailbox, and the Receive mailbox can be initialized in a function
block (as with SINEC L1, see Section 12.2.3).
If too much data is transferred, the reaction is the same as for "Overflow" on the SINEC L1 local
area network.
Differences between Point-to-Point Connection and CP 530
In a point-to-point connection, data is written directly into the CPU's program memory. The
control program can therefore access this area only between the time the data has been received
and the next frame enabled.
These steps must be coordinated over the control program.
When using a CP 530, the data in a frame is initially stored in a CP 530 buffer.
The control program triggers data transfer to the appropriate DBs. Only one read operation is
needed for this transfer. While the control program is processing the DBs, the CP 530 can receive
the next frame.
EWA 4NEB 811 6130-02b
2
0
Error
0: no error
1: send error during last data transfer
Communications Capabilities
12-19
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