HP 8590 E & L Series Spectrum Analyzers and HP 8591C Cable TV ...

� Clear to send (CTS)-Input signal indicates that the external controller is ready to receive
data.
� Data terminal ready (DTR)-Output signal from the spectrum analyzer. When the input buffer
is full, this line goes false.
� Data set ready (DSR)-Is not available.
� Data carrier detect (DCD)-Input to the spectrum analyzer. If DCD is true, the spectrum
analyzer will receive data from the controller. If false, no data will be input. The data will
be ignored.
The spectrum analyzer checks its CTS input before transmitting data to the computer. If the
CTS line is false, the spectrum analyzer will not transmit data. The spectrum analyzer transmits
data when the CTS line is true.
The spectrum analyzer sets the DTR line (PC CTS) false when its input buffer is full.
Baud Rate
The speed at which data is exchanged is called the baud rate or data rate, This is usually
expressed in baud or bits per second. Common baud rates are 1200 and 9600.
Note Some of the programs in this manual use 1200 baud for proper operation. If
your system uses the RS-232 handshake lines, you can use 9600 baud for all of
the programs.
If you need to change the baud rate, refer to the “Setting the Spectrum Analyzer Baud Rate” in
this appendix.
Protocol
The RS-232 protocol is as follows:
Baud rate 300 to 57,000 baud.
8 bits per character.
1 stop bit.
No parity.
Software handshake-none.
Xon/Xoff and ENQ/ACK not supported by the spectrum analyzer.
When BREAK is issued to the spectrum analyzer, the following occurs:
1. The present command is aborted.
2. The input buffer is cleared.
3. The output buffer is cleared.
4. All trace output is stopped.
5. The command parser is reinitialized.
BREAK does not perform any of the following:
� Invoke instrument preset.
� Clear SRQ off screen.
H Clear illegal command off screen.
The RTS signal goes true on power-up and does not go false during any communication. It stays
true while power is on.
Figure C-2 and Figure C-3 lists the signal connections between a personal computer and the
spectrum analyzer.
C-2 RS-232 and Parallel Option 043