33
RS-232 Interface
RS-232 Interface Connector
The 9
−
way D
−
type serial interface connector is located on the instrument rear panel. The pin
connections are as shown below:
Pin
Name
Description
1
−
No internal connection
2
TXD
Transmitted data from instrument
3
RXD
Received data to instrument
4
−
No internal connection
5
GND
Signal ground
6
−
No internal connection
7
RXD2
Secondary received data (addressable RS-232 only)
8
TXD2
Secondary transmitted data (addressable RS-232 only)
9
GND
Signal ground (addressable RS-232 only)
Single Instrument RS-232 Connections
For single instrument remote control only pins 2, 3 and 5 are connected to the PC. However, for
correct operation links must be made in the connector at the PC end between pins 1, 4 and 6
and between pins 7 and 8, see diagram. Pins 7 and 8 of the instrument must
not
be connected
to the PC, i.e. do not use a fully wired 9–way cable.
Baud Rate is set as described above in Address and Baud Rate Selection; the other parameters
are fixed as follows:
Start Bits: 1
Parity: None
Data Bits: 8
Stop Bits: 1
Addressable RS-232 Connections
For addressable RS-232 operation pins 7, 8 and 9 of the instrument connector are also used.
Using a simple cable assembly, a 'daisy chain' connection system between any number of
instruments, up to the maximum of 32 can be made, as shown below:
The daisy chain consists of the transmit data (TXD), receive date (RXD) and signal ground lines
only. There are no control/handshake lines. This makes XON/XOFF protocol essential and allows
the inter
−
connection between instruments to contain just 3 wires.
