CPU 31x-2 as DP Master/DP Slave and Direct Communication
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PLC S7-300, CPU Specifications CPU 312 IFM to CPU 318-2 DP
A5E00111190-01
Status/Control, Programming via PROFIBUS
As an alternative to the MPI interface, you can program the CPU via
PROFIBUS-DP interface or execute the PG’s Status and Control functions . To do
so, you must enable these functions when configuring the CPU as a DP slave in
STEP 7.
Note
The use of Monitor and Modify via the PROFIBUS-DP interface lengthens the DP
cycle.
Data Transfer Via Transfer Memory
The CPU 31x-2 operating as DP Slave provides a transfer memory for
PROFIBUS DP. The data transfer between the CPU as DP slave and the DP
master always takes place via this intermediate memory. Here you can configure
up to 32 address areas.
That is, the DP Master writes its data to the address areas of the transfer memory
while the CPU’s user program fetches these data and vie versa.
Transfer memory
in the Peripheral
Address Area
PROFIBUS
I/O
CPU 31x-2 as DP Slave
DP master
I/O
Figure 2-4 Transfer Memory in a CPU 31x-2 operating as DP Slave
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