Modbus addressing

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Thread Starter

ParagonIndore

The registers address range for Discrete Input given in the device manual for n=1 is 10001-10004, and for the n=2 10153-10156 Now how to specify the register address in Modbus Request?
 
The "1" digit on the front of the address might be just a "type" indicator. The address of "10001-10004" might be 1 to 4, and for "10153-10156" might be 153 to 156.

Or, it might be 0 to 3 and 152 to 155. The difference is whether you are talking about the protocol address (which starts at 0) or the "data model" address (which starts at 1). The protocol address is what gets sent on the wire. the "data model" address is just a documentation convention.

 
I agree, sounds like a block of addresses. For the first address in a table the protocol reads 0, so offset those addresses (153 - 156 for instance) by -1 and make sure the function (1x table it looks like) and length are correct.
 
That document describes a module which converts between Modbus and TSCNet. According to the document the addressing appears to be predefined.
 
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ParagonIndore

Thank You for your reply.

I know the address is preassigned. That's what i am asking what will be the address for input coil if n=64.
 
According to page 7 of your document, for n=64 the coil address are:

9577-9584 On/Off setting
9585-9592 Operation mode setting
9593-9600 Fan speed setting

etc.

For discrete inputs, input registers, and holding registers, the addresses are similar, except the first digit is not actually part of the address. Rather it is a "type" indicator (0 = coils, 1 = discrete input, 3 = input register, 4 = holding register). This is similar to using "I" for inputs, "Q" for outputs, etc.

Note that the documentation refers to the first address in each case as "1", not "0". A "0" is what gets sent "on the wire" as the protocol for the first address, but the documentation calls this address "1".

I have a brief explanation of Modbus here that you might want to read:
"http://mblogic.sourceforge.net/mbapps/ModbusBasics-en.html"
 
To add to my previous reply, "coils" are read-write and are normally used as outputs. Discrete inputs are read-only, and are normally used as inputs. You said "coil inputs", which seems to be confusing the two types.

For n=64 for discrete inputs:

9577-9580 On/Off setting status
9585-9592 Operation mode status
9593-9600 Fan speed set status

etc.
 
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