Modbus address too large?

bawaller

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Join Date
Feb 2012
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Virginia
Posts
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Hi, I'm replacing a Moscad-L RTU with a ML1100. I've been given a spreadsheet with the modbus addresses I'll need to use for the various points reported to SCADA (WW). The addresses seem like numbers too high, and possibly with too many digits. Are possibly the first 3 digits (ie. 306, 406) not part of the actual data address?
There are multiple moscads, and all have the 306/406 digits, the 3, and 4 making me think input/holding registers. If that is the case, i'm still left with a 4 digit number starting with 6/06, and I don't know how create a register with a number that high. Thanks for your help, much appreciated. -Byron

here's a sample of these addresses:
306152:01
306152:02
306152:03
306152:04
306152:05
306152:06

406664
406664
 
Currently 6-digit addresses are also used to be able to exceed the limit of 9999 addresses per field, example: 46664 becomes 406664


Probably the subfix :01 ...: 06 is used to access individual bits of the 16-bit words
 
The leading numeral 3 or 4 is not part of the Modbus message, never has been.

Those leading numerals are used so human beings can identify the 'memory area' of the register in question.

Leading numeral 3, (3)xxxx or (3)xxxxx is for Input registers. (read only)

Leading numeral 4, (4)xxxx or (4)xxxxx is for Holding registers. (read/write depending on vendors assignment)

(3)xxxx is called 5 digit addressing
(4)xxxxx is called 6 digit addressing



Nowadays, most masters can handle 6 digit register addressing.
 
Thanks for the replies. Yes, the bit addressing makes sense to me. Also, the 3/4 - input/holding registers seems to be as expected. So given that, taking away the 3/4 register designation, I'm left with
306152 -> 06152 (or 6152)

When setting up channel 0 as modbus RTU Slave, I choose a data table file, 9, which create N9 as my input register.

My (limited) experience, is that N9:0 is going to be read at mb 30001.
How can I get as high as 6152? With only 255 elements per table and 3 tables max I believe. Thanks
 
If I had to guess I'd say that while the input registers have addresses up in the 6K's they don't span the whole 6K. In other words, (and this is truly a guess) there probably isn't a "300001" along with a "306152". More than likely you will have to remap you addressing between the PLC and the HMI. It is worth noting, 306152 and 36152 are the same address.
 
There will be something in the comms setup that specifies a starting address and an amount of registers to read/write. So you could set up a 20 word read starting at 306150 for example.

This could be done from either end depending on your setup.
 

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