Re: [Emc-developers] on the integer question by Rene

[Robert S. <rm...@un...>]

Am Montag, dem 08.06.2026 um 09:07 +0800 schrieb Luca Toniolo:
> My worry is that "all numbers are one fungible double" isn't how the 
> systems HAL has to talk to work. IEC 61131-3, CANopen/EtherCAT object
> dictionaries, modbus, OPC UA all keep integer, real and bit-string as
> distinct types with explicit conversion between them. None of them
> has a 
> universal number type.

The modbus I know only has bits and "registers", 16 bit signed
quantities. Everything else is a non-standard extension and there seem
to exist all sorts of combinations of byte-order and bit-width of those
extended data types. modbus is "big endian" and there even are mixed
"big/little" endian mappings of 23bit quantities onto registers.

So in the case of modbus, some sort of component that knows what it is
talking to is needed in any case if you have non-standard quantities.
Also there is no standard discoverable process-data description, the
only thing you can do is try to read an input / coil / register and
look if the address exists.


-- 
Robert Schöftner <rm...@un...>