Chapter 3 Front-Panel Operation
RS-232 Interface Configuration
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2 When the power supply wants to “talk” over the interface (which means that it has
processed a query) and has received a <new line> message terminator, it will set the
DTR line FALSE. This implies that once a query has been sent to the power supply,
the bus controller should read the response before attempting to send more data. It
also means that a <new line> must terminate the command string. After the response
has been output, the power supply sets the DTR line TRUE again, unless the first case
(see above) prevents this.
The power supply monitors the DSR line to determine when the bus controller is
ready to accept data over the interface. The power supply monitors the DSR line
(pin 6 on the RS-232 connector) before each character is sent. The output is
suspended if the DSR line is FALSE. When the DSR line goes TRUE, transmission
will resume.
The power supply holds the DTR line FALSE while output is suspended. A form
of interface deadlock exists until the bus controller asserts the DSR line TRUE to
allow the power supply to complete the transmission. You can break the interface
deadlock by sending the <Ctrl-C> character, which clears the operation in progress
and discards pending output (this is equivalent to the IEEE-488 device clear action).
For the <Ctrl-C> character to be recognized reliably by the power supply while it
holds DTR FALSE, the bus controller must first set DSR FALSE.
RS-232 Troubleshooting
Here are a few things to check if you are having problems communicating over the
RS-232 interface. If you need additional help, refer to the documentation that came
with your computer.
• Verify that the power supply and your computer are configured for the same baud
rate, parity, and number of data bits. Make sure that your computer is set up for 1
start bit and 2 stop bits (these values are fixed on the power supply).
• Make sure to execute the SYSTem:REMote command to place the power supply
in the remote mode.
• Verify that you have connected the correct interface cable and adapters. Even if
the cable has the proper connectors for your system, the internal wiring may be
incorrect. The Agilent 34398A Cable Kit can be used to connect the power supply
to most computers or terminals.
• Verify that you have connected the interface cable to the correct serial port on your
computer (COM1, COM2, etc.).
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