VIPA CP 240 RS232, Manual

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Chapter 4 CP 240 - serial Manual VIPA System 200V
4-34 HB97E - CP - Rev. 11/30
At deployment of multiple slaves with RS485 there cannot occur bus
conflict errors because the master may only communicate with one slave at
a time. The master sends a command telegram to the save specified via
the address and waits for a certain time where within the slave may send
its respond telegram. During the latency communication with another slave
is not possible.
For the communication with multiple slaves every slave needs a SEND
data block for the command telegram and a RECEIVE data block for the
respond telegram.
An application with several slaves would be consisting of an according
amount of data blocks with commands.
These are executed in sequence:
1. slave: Send command telegram to slave address 1.slave
Receive respond telegram from slave address 1.slave
Interpret respond telegram
2. slave: Send command telegram to slave address 2.slave
Receive respond telegram from slave address 2.slave
Interpret respond telegram
... etc.
A request may be send to on specified slave or as broadcast message to
all slaves. To mark a broadcast message the slave address is set to 0.
Only write commands may be sent as broadcast.
Note!
After a broadcast the master is not waiting for a respond telegram.
If you "OR" the FC 0 parameter ANZ with 4000h the slave data to send
were not transferred to the master input area but to the master output area.
Since this area can be read by the master by means of function codes this
functionality can be used for example for the direct error transmission to
the master.
Access to multiple
slaves
Write to master
output area