Keithley 7999-4, Instruction Manual

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Connections 2-5
Connections
RS-232 Connection
The RS-232 serial port is connected to the serial port of a computer (controller) using a
straight-through RS-232 cable terminated with DB-9 connectors. Do not use a null modem
cable. The serial port uses the transmit (TXD), receive (RXD), and signal ground (GND) line
of the RS-232 standard. Figure 2-3 shows the Model 7999-4 connector with Table 2-1 contain-
ing the pinouts for the connector.
If your computer uses a DB-25 connector for the RS-232 interface, an additional cable or
adapter (DB-25 to DB-9) is required.
NOTE In the RS-232 interface, only pins 2, 3, and 5 are used. Pins 7 and 8 are tied together,
but not connected to the circuit board. Pins 1, 4, and 6 are also tied together and not
connected to the circuit board.
Table 2-1
RS-232 connector terminals
Pin Number Description
1 Tied to pins 4 and 6
2 TXD, Transmit data
3 RXD, Receive data
4 Tied to pins 1 and 6
5 GND, Signal ground
6 Tied to pins 1 and 4
7 Tied to pin 8
8 Tied to pin 7
9 Not used
RS232
9 8 7 6
5 4 3 2 1
Figure 2-3
RS-232 interface
connector