CMU Hardware Interfaces 
1100.4903.12 8.5  E-8 
Serial Interfaces (COM 1, COM 2) 
The CMU is equipped with two serial RS-232-C interfaces. The two assigned 9-pin standard Sub-D 
male connectors are designated with COM 1 and COM 2 and located on the rear panel. A controller 
can be connected via this interface for remote control. 
The two RS-232 interfaces provide two independent channels which can be active simultaneously. 
However, setting commands and queries act on the same device hardware. The interfaces are 
activated and configured in the Setup - Remote menu or via remote control using the commands 
SYSTem:COMMunicate... 
 
 
 
Interface characteristics 
!  Serial data transmission in asynchronous mode, 
!  Bidirectional data transmission via two separate lines, 
!  Transmission rate selectable from 110 to 115200 baud, 
!  Logic 0 signal from +3 V to +15 V, 
!  Logic 1 signal from -15 V to -3 V, 
!  An external instrument (controller) can be connected, 
!  Hardware handshake RTS/CTS or software handshake XON/XOFF can be selected. 
 
12345
67
89
DCDTxD
RxDDTR
GND
RI
CTS
RTS
DSR
 
  Fig. 8-2   Pin assignment of the RS-232-C interface 
 
Designation  Abbreviation  Pin (9-pin male)  Pin (25-pin male) 
Data Carrier Detect  DCD  1  8 
Receive Data  RxD  2  3 
Transmit Data  TxD  3  2 
Data Terminal Ready  DTR  4  20 
Signal Ground  GND  5  7 
Data Set Ready  DSR  6  6 
Request To Send  RTS  7  4 
Clear To Send  CTS  8  5 
Ring Indicator  RI  9  22