COMMUNICATIONS TROUBLESHOOTING
GUIDELINES
Always start troubleshooting by sending from the machine control to DNC. The DNC software is much more flexible in how it receives data and will not issue an "alarm" like a machine control. The nature of the data received may help you identify the source of the problem.
Follow
these steps if you are having a problem communicating with the machine
control.
1.
With DNC in Terminal mode send a program from the machine control to
the PC.
If
the machine "alarms":
The
cable may not be connected to the correct port at the machine control. Check
the cable configuration at the machine end, particularly pins 6, 8, and 20.
If
the machine acts like it is prepared to send but "sits" continuously
in send mode:
A
file will not be sent if the CTS line (line 4 or 5 depending on the machine
configuration) is not asserted. The cable should have a jumper between pins 4
& 5, or lines 4 and 5 should pass through to their compliment lines on the
computer end.
If
the machine looks like it is trying to send but you receive nothing:
Check
the cable. Pins 2 and 3 may need to be swapped to match the send/receive lines
on the machine control with the receive/send lines on the computer. If
hardware handshaking is being used and pins 2 and 3 need to be swapped pins 4
and 5 will also need to be swapped.
Check
to see that the correct port has been selected. A quick test is to unplug the
cable while trying to send. If an alarm is shown, then the correct port is
being addressed.
Check
the DNC communications parameters to be sure the correct COM port has been
selected.
Try
sending to DNC from another machine control or another computer to verify the
COM port is not defective.
If
"garbage" prints out on the computer screen while receiving:
The communications
parameters are probably mismatched. Check to see that the data types (ISO, EIA,
or ASCII) match. Many machines have a parameter or setting to select between
EIA and ISO. Then check the baud rate.
Other
possible sources of "garbage" are long cables, cables with weak
connections, cables running near EMF sources, or ground faults.
2.
Once data has been successfully received most cable, machine
parameters, and COM port configuration problems have been eliminated.
Now send from DNC to the
machine control. If DNC appears to send the file but the machine acts like it
is not receiving:
Check the file contents.
Perform the initial tests with a file which has been received from the
control, not one generated on your CAD/CAM system. Some controls require an
end of block at the beginning of the file or require a program qualifier (like
02213) at the beginning of the file. Others require a M30, M02, %, or END at
the end of the file.
If
a partial program is received, blocks of data appear to be dropped, or the
machine issues a data overflow alarm:
Check to make sure handshaking has been properly enabled. If the cable uses only lines 2,3 and 7 select X-ON/X-OFF protocol. (Also referred to as Software Handshaking or DC1/DC3 control codes.) If the machine does not support software handshaking use a cable with pins 4 and 5 connected. This will enable CTS/RTS handshaking.