7
Parity
None - eight data bits without parity
Even - seven data bits with even parity
Odd - seven data bits with odd parity
RS-232 Flow Control
The RS-232 interface supports the following flow control options. For each case, the electronic load will
send a maximum of five characters after hold-off is asserted by the controller. The electronic load is
capable of receiving as many as fifteen additional characters after it asserts hold-off.
• The electronic load asserts its Request to Send (RTS) line to signal hold-off when its input buffer
is almost full, and it interprets its Clear to Send (CTS) line as a hold-off signal from the
controller.
• When the input queue of the electronic load becomes more than ¾ full, the instrument issues
an X-OFF command. The control program should respond to this and stop sending characters
until the electronic load issues the X-ON, which it will do once its input buffer has dropped
below half-full. The electronic load recognizes X_ON and X_OFF sent from the controller. An X-
OFF will cause the electronic load to stop outputting characters until it sees an X-ON.
• NONE: There is no flow control.
Flow control options are stored in non-volatile memory.
RS-232 Connections
The RS-232 serial port can be connected to the serial port of a controller (i.e., personal computer) using
a null modem RS-232 cable terminated with DB-9 connectors. Figure 1 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 straight-through
(not null modem) cable.
Figure 1 - RS-232 Connector Pinout
Pin Signal Description
3 RXD Receive Data
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