Siemens SIMATIC S7-300 Hardware And Installation Manual page 61

The CPU automatically broadcasts its bus parameter configuration (e.g.
transmission rate) via MPI interface. This means that a programming device, for
example, can automatically "hook up" to an MPI subnet.
Note
You may only connect one PG to the MPI subnet in run mode. You must not
connect other nodes (e.g. OP, PP, TD, ...) to the MPI subnet, because due to line
noise you might loose global data packets or transmitted data.
PROFIBUS-DP interface
The PROFIBUS-DP interface is mainly used to connect distributed I/O.
PROFIBUS-DP allows you to create large subnets. The maximum possible
PROFIBUS transmission rate is 12 Mbps. The CPU broadcasts its bus parameter
configuration (e.g. transmission rate) via PROFIBUS-DP interface. This means that
a programming device, for example, can automatically "hook up" to a PROFIBUS-
DP subnet. In your configuration you can specify to disable bus parameter
broadcasting. CPUs 313C-2 DP and 314C-2 DP are equipped with a second
interface, an RS485 PROFIBUS-DP interface that you can configure as master or
slave.
PtP interface
At the CPU's PtP interface you can connect devices equipped with a serial port,
e.g. barcode readers, printers, ..., (non-Siemens devices). Here, you can operate
with transmission rates in full duplex mode (RS422) up to 19.2 Kbps, and in half
duplex mode (RS485) up to 38.4 Kbps. CPUs 313C-2 PtP and 314C-2 PtP are
equipped with a second interface, namely a PtP interface (Point-to-Point, 15-pin).
The following PtP communication drivers are implemented in these CPUs:
• ASCII driver
• 3964 (R) protocol
• RK512 (only CPU 314C-2 PtP)
S7-300 Programmable Controller Hardware and Installation
A5E00105492-01
Configuring
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