Siemens SIMATIC S7-300 Hardware And Installation Manual page 66

Configuring
PROFIBUS DP interface
Availability: CPU types with the identifier "DP" (used as a DP master)
The PROFIBUS DP interface is mainly used to connect distributed I/Os.
PROFIBUS DP allows you to create large, extended subnets, for example.
The PROFIBUS DP interface can be configured as either master or slave, and
offers a transmission speed of up to 12 Mbps.
The CPU sends its bus parameters (e.g. the baud rate) to the PROFIBUS DP
interface (if it is used as the master). A programming device, for example, can then
automatically retrieve the correct parameters and connect to a PROFIBUS subnet.
In your configuration, you can disable this bus parameter broadcast.
Note
(For the DP interface in slave mode).
If you have disabled the Commissioning / Test mode check box in the DP interface
properties in STEP 7, the baud rate you have set will be ignored, and the master's
baud rate will be used automatically,
Cross-reference
For information on the new DPV1 functionality, see the section with the same name
in the CPU Data Reference Manual, CPU 31xC and CPU 31x.
PtP interface
Availability: CPU types with the identifier "PtP".
You can use the PtP (Point to Point) interface on your CPU to connect external
devices such as a barcode reader, printer, etc. to a serial port. Baud rates of up to
19.2 Kbps for full duplex (RS 422) and up to 38.4 Kbps for half duplex (RS 485) are
possible.
The following PtP communication drivers are installed in the CPUs:
• ASCII driver
• 3964 (R) protocol
• RK512 (only CPU 314C-2 PtP)
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S7-300 Programmable Controller Hardware and Installation
A5E00105492-02