VIPA CP 240 RS232, Manual

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Chapter 4 CP 240 - serial Manual VIPA System 200V
4-16 HB97E - CP - Rev. 11/30
ASCII / STX/ETX / 3964(R) / RK512 - Communication principle
The serial communication happens via the deployment of handling blocks
in the PLC user application. These handling blocks may be downloaded
from ftp.vipa.de or received as part of the CD-ROM VIPA "ToolDemo".
Depending on the protocol the following handling blocks are used:
ASCII STX
3964
RK512 Modbus FC Name
x x x FC0 SEND_ASCII_STX_3964
x x x FC1 RECEIVE_ASCII_3964
x FC2 FETCH_RK512
x FC3 SEND_RK512
x FC4 S/R_ALL_RK512
x x x FC9 SYNCHRON_RESET
x FC11 ASCII_FRAGMENT
Note!
A communication with SEND and RECEIVE blocks is only possible if the
parameter ANL of the SYNCHRON block has been set in the start-up-OB
before.
Data that is written into the according data channel by the CPU via the
back plane bus are written into the according send buffer (1024Byte) by the
communication processor and from here put out via the interface.
When the communication processor receives data via the interface, the
data is stored in a ring buffer (1024Byte). The CPU via the data channel
may read the received data.
The exchange of received telegrams via the back plane bus happens
asynchronously. When a complete telegram has arrived via the serial
interface (expiration of the ZVZ), this is stored in a ring buffer of 1024Byte.
The length of the ring buffer determines the max. length of a telegram.
There may be stored up to 250 telegrams according to the
parameterization whereby their overall length may not exceed 1024.
When the buffer is filled up, new telegrams are rejected. A complete
telegram is divided into blocks of 12Byte and transferred to the back plane
bus. The reassembly of the data blocks has to take place inside the CPU.
With ASCII-fragmented incoming data of a telegram is in blocks
immediately transferred to the CPU. Here the block length is at least
12Byte. At ASCII-fragmented the CP doesn’t wait until the complete
telegram has been received.
Communication
via handling
blocks
Send and receive
data
Communication
via back plane bus
Communication with
ASCII-fragmented