Configuration
4.9 Serial interface
CP 1243-8 IRC
Operating Instructions, 02/2018, C79000-G8976-C385-03
79
Acknowledgment mechanism for the IEC protocol
With each sent data frame, the CP sends a continuous send sequence number. The data
frame remains initially stored in the send buffer.
When it receives the data frame, the master sends the send sequence number from this or
(if several frames are received) the last frame as an acknowledgement to the CP. The CP
saves the send sequence number returned by the master as a receive sequence number
and uses it as an acknowledgement.
Frames whose send sequence number is equal to or lower than the current receive
sequence number are evaluated as having been successfully transferred and are deleted
from the send buffer of the CP.
Recommendations of the specification:
● w should not be higher than 2/3 of k.
● Recommended value for k: 12
● Recommended value for w: 8
Access to the Web server
Access to the Web server of the CPU
The Web server of the S7-1200 station is located in the CPU. Via the CP, you have access
to the Web server of the CPU.
From a PC you can access the Web server of the station if the PC is connected to the
system network via LAN.
You will find information on the Web server in the manual /1/ (Page 225).
Configuration of the serial interface
The serial interface can only be used for communication using the ST7 protocol.
The physical connector for the serial interface is located on the left-hand side of the CP, see
section Serial connection for TS module (Page 46).
For connection to the network you require a suitable TS module, refer to the appendix TS
modules (Page 193).
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