BK Precision MDL4U Series, User Manual, Page: 63 / 68

Operations 63
RS232 Connections
The RS-232 serial port can be connected to the serial port of a controller (i.e., personal computer) using a straight-
through RS-232 cable terminated with DB-9 connectors. Do not use a null modem cable. Figure 33 shows the pinout
for the connector.
If your computer uses a DB-25 connector for the RS-232 interface, you will need a cable or adapter with a DB-25
connector on one end and a DB-9 connector on the other. It must be a straightthrough (not null modem) a cable.
Figure 4.19 DB9 Pinout
Pin Number Signal Function
1 NC No Connection
2 TXD Transmit Data
3 RXD Receive Data
4 NC No Connection
5 GND Ground
6 NC No Connection
7 CTS Clear to Send
8 RTS Ready to Send
9 NC No Connection
Table 4.7 DB9 Pinout
RS232 Troubleshooting
If you are having trouble communicating over the RS-232 interface, check the following:
• The computer and the electronic load must be configured for the same baud rate, parity, number of data bits, and
flow control options. Note that the electronic load is configured for 1 start bit and 1 stop bit (these values are fixed).
• The correct interface cables or adapters must be used, as described under the RS-232 connector. Note that even if
the cable has the proper connectors for your system, the internal wiring may be incorrect.
• The interface cable must be connected to the correct serial port on your computer (COM1, COM2, etc.) and the
correct 9-pin serial port on the mainframe.
Communication Settings
Before communicating, please make sure that the following parameters of the electronic load match that of the PC. You
can enter the System menu (Shift + ) to make any changes.
Baud rate : 9600 (5800, 9600, 19200, 38400, 57600, 115200)
Data bit : 8
Stop bit : 1
Parity : None (None, Even, Odd)
Local address : 0 (0 through 31, default setting is 0)
Note:
When communicating with a PC, you can only use one communication interface at a time.