Wingpath to cease trading on 25 October 2025
From 25 October 2025 we will no longer be selling licences for our software products (ModSnmp, ModMultiSim, Modsak, ModSlaveSim, ModMaster and ModTest).
The website will remain operational until at least 2027 for reference purposes, and for the registration and transfer of product licences.
Modsak Manual v3.16 - 2.3. Address mapping
As explained in section 4.3 of the current Modbus specification, the Modbus protocol uses four different address ranges (called "tables" in the specification): discrete inputs, coils, input registers, and holding registers. The function code of a message determines to which address range the address in the message belongs. The address ranges may be separate, or they may be overlaid so that a register may appear in more than one address range. Note that the specification says nothing about how the overlaying is done - in particular, there is no mention of the byte-ordering issues involved.