Siemens SIMATIC 500 Series Description And Operating Instructions page 6

Setting the CPU Dipswitches (continued)
Communications
Port 1
Port 1
Port 2
Communications
Port 2
Installing 505 System Hardware
3-24
The 545 and 555 CPUs have two communications ports. Both ports are
configured as Data Terminal Equipment (DTE).
SW2 selects Port 1 as either a programming port or a printer port on a
545/555 CPU. Port 1 uses an RS-232/RS-423 signaling protocol and an
RS-232 pinout arrangement with an RS-423 (+5 V) signal level extending
up to 50 feet (15 m). You can use a modem to extend this distance.
•
Setting SW2 to the left selects Port 1 as a programming port.
•
Setting SW2 to the right selects Port 1 as a printer port.
Figure 3-13 shows the locations of Port 1 and Port 2 on the front of the CPU.
Port 1
RS-232 Port Pinouts RS-232 Port Pinouts
Controller
Male 9-Pin D Type Male 9-Pin D Type
Pin Signal
1 RSD
2 RCV
3 XMT
(3)
4 DTR
5 GND
6 DSR
7 RTS
(1) Dipswitch 1 is On.
(2) Dipswitch 1 is Off.
8 CTS
(3) User connection to select RS-232 operation.
Figure 3-13 545/555 CPU Port Locations
With the 545 and 555 CPUs, your choice of cabling determines whether
Port 2 functions as an RS-232/RS-423 port or as an RS-422/RS-485 port.
Figure 3-13 describes the pinouts required for the various Port 2 options.
If you use RS-422/RS-485 cabling, SW1 on the dipswitch allows you to select
between RS-422 and RS-485. Use SW1 as follows:
•
Set SW1 to the left when you use RS-232 or RS-422 cabling.
•
Set SW1 to to the right when you use RS-485 cabling. RS-485 uses a
single twisted pair to transmit and receive data between the
programming device and the 545/555 CPU. Multiple CPUs or multiple
programming devices (on this RS-485 link) are not supported and must
not be used.
(1)
Port 2
Port 2
RS-422 Port Pinouts
Controller Controller
Male 9-Pin D Type
Pin Signal Pin Signal
2 RCV 3
3 XMT 9
5 GND 5
6 SEL232* 8
2
(1) Port 2
RS-485 Port Pinouts
Controller
Male 9-Pin D Type
Pin Signal
DO+ 3
DI+ 8
GND 5
6
DO–
DI–
6 SEL232*
120 W termination resistors
can be used for higher noise
immunity and more reliable
long-distance communication.
SIMATIC 545/555/575 System Manual
(2)
TX/RX+
TX/RX–
GND
SEL232*