M340 Addressing

Hey,

I have a structure I want to make accessible over the network (ModbusTCP). I've assigned a modbus address to the structure and it auto populated the addresses.

What I am wondering is how does it pack the BOOL data type into the MW? I noticed it uses the same MW address for two boolean registers. How do I access those bits when I unpack the word? Is bit 0 the first boolean and bit 1 the second boolean?

Thanks

I believe each BOOL takes one byte (8 bits) to store, hence two BOOLs per 16 bit word. From memory the first bit of each byte is the value. If they were EBOOLs then other bits would indicate forcing, previous state etc

Saffa said:

I believe each BOOL takes one byte (8 bits) to store, hence two BOOLs per 16 bit word. From memory the first bit of each byte is the value. If they were EBOOLs then other bits would indicate forcing, previous state etc

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So you're saying the BOOL data should be in bit 0 and bit 8 of each word?

That would be where I would look first. I have a little project next week with an M340, I'll take a look at how it works then.