Just a little amplification to what Ed has said -

   I've worked with 3-wire RS232 for 27 years.- 8-N-1 (Xon/Xoff).

   If Tracy is using the standard RS232 wiring convention for the serial
connection, the TX is pin 2, RX is pin 3, but signal ground is not pin 1,
it is pin 7 (DB25 connector) or pin 5 (DB9 connector).  The ground on
pin 1 of the DB25 is "frame ground" and "signal ground" is not
necessarily connected to it (indeed, it ~shouldn't~ be.) 

Best Regards,
Dale R.


Ed Anderson wrote:

As best I recall, In the programming world, its a mnemonic used to mean "No Operation"= NOP, in other words is was a line of code that used up a clock cycle(s) of the chip but actually did nothing.  Sometimes used for timing purposes.

 

I think Tracy uses it to mean No Operation.   The link between the EC2 and the EM2 is via three wires, two wires over which data and control pulses flow and the all important ground wire.  If do not have a good electrical ground between your EM2 and EC2 the serial communication function will not operate properly or may be sporadic.  Since you have power to your EM2, I would check and see that it has a good ground to the EC2.

 

 

Ed