Section 4 - RS232 Communication
The RS232 communications port allows bi-directional data transfer via a three
conductor cable consisting of signal ground, receive input, and transmit output.
It is recommended that less than fifty feet of cable be used between the computer
and this instrument.* Note that multiple instruments cannot be tied to the same
port in this configuration. The RS232 port is optically isolated to eliminate
ground loop problems.
Below is a pinout diagram for the serial port of the BB701 as well as the pinout
for a 9-pin PC serial port. Use a straight DB9 (female) to DB9 (male) connector
cable to connect your computer to the BB701. The cable should be attached only
when the computer and BB701 are off.
Only parameters in the parameter list should be modified or queried via the
serial port. Other parameters can be viewed or queried from the controller,
directly. It is highly recommended that baud rate for the controller be modified
on the controller, directly. Note that both the BB701 and the computer must be
communicating with the same serial communications parameters to establish a
working communication link.
The serial communications feature can be tested using any standard terminal
emulation package. Note that this controller does not time out waiting for the
next character to be transmitted. Be sure not to use the XON/XOFF or hardware
handshaking. Lastly, it should be noted that following a complete transmission
to the BB701, a response is sent back. If the message was valid, the changed or
queried parameter is echoed back (following the same format). If the message
was not according to acceptable format or was attempting to force a parameter
out of range, an “ERROR” message is echoed.
*This will assure performance of the BB701 within the CISPR11/EN55011:1991
standards, under the E. M. C.
Figure 8. Connecting the BB701 to a Computer’s Serial Port
4-1
BB701
4
1
6
7
8
9
6
7
8
9
2
3
4
5
1
2
3
4
5
RX
TX
GND
TX
RX
GND
BB701
BLACKBODY
CALIBRATOR
COMPUTER
SERIAL
PORT
(RS232)
