Remote Interface Reference 4
Keysight 34420A User’s Guide 195
The meter sets the DTR line FALSE in the following cases:
1 When the meter’s input buffer is full (when approximately 100 characters have
been received), it sets the DTR line FALSE (pin 4 on the RS-232 connector).
When enough characters have been removed to make space in the input
buffer, the meter sets the DTR line TRUE, unless the second case (see below)
prevents this.
2 When the meter 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
meter, the 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 meter sets the DTR line TRUE again,
unless the first case (see above) prevents this.
The meter monitors the DSR line to determine when the controller is ready to
accept data over the interface. The meter 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 meter 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 meter to complete the transmission. You break the interface
deadlock by sending the <Ctrl-C> character, which clears the operation in
progress and discards pending output (this is equivalent the the IEEE-488
device clear action).
RS-232 Troubleshooting
Here are a few things to check if you are having problems using the RS-232
interface. If you need additional help, refer to the documentation that came with
your computer.
– Verify that the meter 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 meter).
– Make sure to execute the SYSTEM:REMOTE command to place the meter in
the REMOTE mode.
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