Modbus TCP/IP Help

Question

Hello Labviewers,
So I just hooked up a couple of Honeywell UDA2182 controllers to my computer using an ethernet connection.  I've established communications using modbus (specifically the Datalogging and Supervisory Control module's Modbus I/O server option) and I can tell that readings are coming through to the computer.  
My problem is that it's all in some weird alien langauge.  I can't tell which parameters I'm viewing data for, and the data that my computer is recieving are crazy huge numbers that don't relate to anything.  My guess is that I'm supposed to somehow convert these numbers but I'm not sure how to go about it.
Thanks for any and all help/advice,
Mike
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Answer 1

Hi Everyone!
Thanks so much for the help thus far.  When I first hooked up the PLC I was indeed hoping for and expecting simple, easy to understand human readable numbers like 7.07 or 13.72.  After reading through everyone's replies this morning, I have spent the better part of the day reading up on Modbus and going back through the manual that came with the PLC.  Things are starting to make sense a little more but I still need any help you might offer.
I've figured out that I want to read registers (decimal addresses) 30001, 30003, 30005, and 30007.  I should be able to communicate with these registers via Modbus function code 04, although, it is unclear as to whether I need to specify this function code seeing as how I'm using a Modbus I/O server in continuous operation (rather than sending one request and receiving one response at a time).  These 4 registers are all classifies as type = float and I see in my manual that is says "floating point values require two consecutive registers".  I am now assuming that to accurately read the data associated with register 30001, I will need to read and convert data from 30001 and 30002.
Further, it appears to me that Labview wishes to represent these register addresses with an extra 0, making 30001 -> 300001?  Earlier this morning, using the DSC module's Modbus I/O server I was able to monitor register 300001 in the Distributed System Manager.  The values reported to me were as follows (can choose any representation): 16,609(decimal); 1.6609000e+04(scientific); 40E1(hex); 40340(octal); and 100000011100001(binary).  I was expecting a value of 7.07 (pH units) but as this is only the single register 300001 perhaps these values are only half of the human readable answer.  
According to my controller's manual the default setting for communications is Word Swap = yes, or Big Endian, byte order 4,3,2,1.  However, this can be changed on the controller should I need to set this parameter to Little Endian.  There is also a section in the manual regarding IEEE 32-bit floating point stuff where a formula is given for calculating the floating point number from a 23 bit signed binary with 8 bit biased binary exponent.  I will admit that this formula makes no sense but I'm willing to give it a shot if needs be.  The crazy terminology here (mantissa, Endian, etc.) has really been difficult to assimilate.  
My goal now is to try and read registers 300001 and 300002 and somehow combine the two values to produce a final human readable number?  Does it seem like I'm on the right track?  Does anyone have any advice as to how to combine these two register values?  Thanks again.  I'll report back soon.
-Mike