Multi point interface
The Multi Point Interface (MPI) is an interface or the MPI bus is a proprietary interface of Simatic S7 devices from Siemens and is used to connect PGs ( programming devices ), OPs ( operating devices / operator panels ) and other Simatic S7 Devices used.
The MPI interface is based on the EIA-485 standard (formerly RS-485 ) and works as standard with a transmission rate of 187.5 k baud . Other transfer rates that can be set depending on the access adapter or Simatic device are between 19.2 kbaud and 1.5 Mbaud.
MPI is hardware- compatible with the PROFIBUS interface of the Siemens PLC , but in contrast to this, it is often not electrically isolated.
| Pin assignment of the SUBD9 connector: | ||
|---|---|---|
| Pin1 | (Umbrella) | |
| Pin2 | Gnd (M24V) | |
| Pin3 | Data B + | *) |
| Pin4 | RTS AS | *) |
| Pin5 | Gnd (M5V) | *) |
| Pin6 | +5 V | |
| Pin7 | +24 V | |
| Pin8 | Data A- | *) |
| Pin9 | RTS PG | |
Note *) required for programming cable
The bus connector for the (2-wire) Profibus cable contains a (switchable) resistor network for the bus termination with: 220 Ohm between the signal wires A- and B + and 390 Ohm each between A- and Gnd, or B + and +5 V.
Various manufacturers also offer PCI plug-in cards, PCMCIA plug-in cards, USB adapters or Ethernet adapters for communication via MPI .
literature
- Siemens: SIMATIC PG / PC - PROFIBUS PC Adapter USB A2 Operating Instructions [1]
See also
- Point to Point Interface (PPI), an equally proprietary interface based on EIA-485 for small Simatic devices
Web links
- libnodave a free library for communication with Siemens PLC under Windows / Linux