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Read Only Access When Dynamically Addressing Booleans

Why does the TOP Server Modbus driver not permit writes to the same items that another IO Server is able to write to?

In order to maintain maximum flexibility the with different client applications and devices, the TOP Server does not require a fixed address length for standard Modbus addressing. 

The most significant digit in the TOP Server Static or Dynamic address designates the Primary Table.

Primary Table

Description

0

Output Coils

1

Input Coils

3

Internal Registers

4

Holding Registers

If a client is dynamically addressing Output Coils without a zero as the most significant digit, the request will either be rejected by the TOP Server ('Attempt to add Item Failed' for output coils with 2, 5, 6, 7, 8, or 9 as the most significant digit) or mistaken as another primary table.  If the item begins with 1 or 3 then writes to the address will be rejected as Input Coils and Internal Registers are read only.  If the Item begins with 4, then the address may authenticate but return an incorrect value.

In order to resolve this, append the Item in the client with a 0 as the most significant digit.

Original:   579
After Padding:   0579

Additional zeros may be added if a uniform length is desired.  However, this is not required by TOP Server.