Chapter 4 Remote Operation and Programming
Tips on Using the RS-232C Port on the 5071A
66 Operating and Programming Manual
The 5071A will then wait until it receives an XON signal (Control-Q) before
resuming the transmission. The 5071A will wait indefinitely for an XOFF to
clear.
Example:
One example of this is when the 5071A is printing the Status Log and the
connected printer runs out of paper. If the printer uses the XON/XOFF protocol,
it will send an XOFF (Control-S) that will stop the flow of data from the 5071A.
The front panel is now busy waiting for an XON (Control-Q) to resume printing.
Solution:
If the front panel is locked in a print operation to the Serial Port, the solution is to
correct the cause of the problem. For example, add more paper to the printer.
If the printer is no longer connected but a terminal is available, ensure that the
terminals Baud Rate, Parity, Data Bits, and Stop Bits are consistent with the
5071A, then send a Control-Q from the terminal keyboard. This should result in
the remaining data from the 5071A being sent to the terminal and thereby clear
the problem.
DSR
The DSR signal acts exactly like the XON/XOFF protocol, but instead of being
implemented in software it is done in hardware. The DSR line (pin 6) is one of
the three signals used by the 5071A in RS-232C communications (the other lines
are Data Transmit and Data Receive). When DSR is false (negative voltage), data
transmission from the 5071A will stop until the DSR is true again (positive
voltage). If this line is not connected to any signal, then DSR is pulled positive
inside the 5071A.
Example:
One example of how DSR can stop front panel operation is if the wrong cable is
used, forcing a negative signal on the DSR (pin 6). If under these conditions, an
INFO PRINT command is issued from the front panel, the 5071A will be busy
until the DSR returns to a positive voltage.
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