Using The Em Dp01 To Connect An S7-200 Smart As A Dp Device - Siemens Simatic S7 Series System Manual

Communication
8.5 PROFIBUS
A DP master is configured to know the addresses, DP device types, and any parameter
assignment information that the DP devices require. The DP master is also told where to
place data that is read from the DP devices (inputs) and where to get the data to write to the
DP devices (outputs). The DP master establishes the network and then initializes its
DP devices. The DP master writes the parameter assignment information and I/O
configuration to the DP device. The DP master then reads the diagnostics from the
DP device to verify that the DP device accepted the parameters and the I/O configuration.
The DP master then begins to exchange I/O data with the DP device. Each transaction with
the DP device writes outputs and reads inputs. The data exchange mode continues
indefinitely. The DP devices can notify the DP master if there is an exception condition, and
the DP master then reads the diagnostic information from the DP device.
Once a DP master has written the parameters and I/O configuration to a DP device, and the
DP device has accepted the parameters and configuration from the DP master, the
DP master owns that DP device. The DP device only accepts write requests from the
DP master that owns it. Other DP masters on the network can read the DP device's inputs
and outputs, but they cannot write anything to the DP device.
8.5.1.2

Using the EM DP01 to connect an S7-200 SMART as a DP device

The S7-200 SMART CPU can be connected to a PROFIBUS DP network through the
EM DP01 PROFIBUS DP module. The EM DP01 is connected to the S7-200 SMART CPU
as an expansion module. The PROFIBUS network is connected to the EM DP01
PROFIBUS DP module through its DP communications port. This port operates at any
PROFIBUS baud rate between 9600 baud and 12 Mbaud. Refer to the
EM DP01 PROFIBUS DP module Technical Specifications for the baud rates supported.
As a PROFIBUS DP device, the EM DP01 accepts several different I/O configurations from
the DP master, allowing you to tailor the amount of data transferred to meet the
requirements of the application. Unlike many DP devices, the EM DP01 does not transfer
only I/O data. The EM DP01 also transfers inputs, counter values, timer values, or any other
values that you move to the variable memory in the S7-200 SMART CPU. Likewise, the
EM DP01 transfers data from the DP master to the variable memory in the S7-200 SMART
CPU. You can then move this data from variable memory to other data areas.
The DP port of the EM DP01 PROFIBUS DP module can be attached to a DP master on the
network and still communicate as an MPI device with other master devices such as SIMATIC
HMI devices or S7-300 / S7-400 CPUs on the same network. The following figure shows a
PROFIBUS network with an S7-200 SMART CPU SR20 and an EM DP01 PROFIBUS DP
module:
● The S7-300 with CPU 315-2 is the DP master and has been configured by a SIMATIC
programming device with STEP 7 programming software. The S7-315-2 DP can read
data from or write data to the EM DP01, from 1 byte up to 244 bytes.
● The S7-200 SMART CPU SR20 is a DP device owned by the CPU 315-2. The ET 200 I/O
module is also a DP device owned by the CPU 315-2.
● The S7-400 CPU is attached to the PROFIBUS network and is reading data from the
CPU SR20 by means of X_GET instructions in the S7-400 CPU user program. (Other
SIMATIC CPUs can use DB1 to access V memory in the S7-200 SMART CPU.)
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