Siemens SIMATIC S5-90U, Системное руководство

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S5-90U/S5-95U Communication via SINEC L1 LAN
14.2 Basic Principle of Data Interchange
Data interchange requires the following mailboxes and bytes to be defined once:
•
A Send Mailbox (SF), containing the data to be sent (max. 64 bytes).
• A Coordination Byte Send (KBS), which is used for coordination between the control program
and SINEC L1.
• A Receive Mailbox (EF), containing the received data (max. 64 bytes).
• A Coordination Byte Receive (KBE), which is used for coordination between the control program
and SINEC L1.
The coordination bytes are located in the flag area and the send and receive mailboxes are usually
stored in a data block. Figure 14-3 shows the interchange of data between two slaves. Seen from
the slave, the exchange of data between the master and the slave functions in the same way. Data
exchange seen from the master is described in detail in the "SINEC L1" manual.
Figure 14-3. Principle of Data Interchange
Source PLC
Receive_Erl
Error
Coordination Byte
Receive (KBE)
(in the flag area)
a a a a a
a a a a a
a a a a a
a a a a a
a a a a a
Destination PLC Slave, e.g. S5-95U
LAN
Coordination Byte
Send (KBS)
(in the flag area)
Send_Erl Error
a a a a a
a a a a a
a a a a a
a a a a a
a a a a a
Receive Mailbox (in the
flag or data area)
Number of net data
L1 source address
Byte 0
Byte 1
Byte 2
.
.
.
.
Byte 65
1 to 64 bytes
net data
Send Mailbox (in the
flag or data area)
Number of net data
L1 destination address
Byte 0
Byte 1
Byte 2
.
.
.
.
Byte 65
1 to 64 bytes
net data
Slave, e.g. S5-95U
Explanation of Figure 14-3:
To send a message, fill in the Send Mailbox. This enables you to specify how much data is to be
sent (number of net data), to address the receiver (L1 destination address) and to store the
message (net data). You then enable sending in the Coordination Byte Send (by setting bit
"Send_Erl).
The S5-95U then sends the message via the local area network to the addressed receiver. After the
sending process, the bit "Send_Erl" is reset by the operating system.
When the message has arrived at the receiver, the bit "Empf_Erl" (receiving enabled) in the
Coordination Byte Receive is reset. The data received is available for evaluation in the Receive
Mailbox.
In order to restore the readiness to receive, you set the bit "Empf_Erl" in the Coordination Byte
Receive after having read the data from the Receive Mailbox.
EWA 4NEB 812 6115-02b
14-3