Agilent Technologies 34401A - Manual (Page 158)

The multimeter holds the DTR line FALSE while output is suspended.
A form of interface deadlock exists until the controller asserts the DSR
line TRUE to allow the multimeter 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 multimeter while it holds DTR
FALSE, the controller must first set DSR FALSE.
In addition, you may have difficulty sending the <Ctrl-C> character if
you are interrupting a query operation, in which case the multimeter
hold the
DTR line FALSE . This may prevent the controller from sending
anything unless you first reprogram the interface to ignore DTR .
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 multimeter 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 multimeter).
• Make sure to execute the SYSTem:REMote command to place the
multimeter 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 not be correct. The Agilent 34398A Cable Kit can
be used to connect the multimeter to most computers or terminals.
• Verify that you have connected the interface cable to the correct
serial port on your computer (
COM 1, COM 2, etc).
Chapter 4 Remote Interface Reference
RS-232 Interface Configuration
152