A Question about Swapping Bytes

[bodoo23]

Now, I am working on a project where I need to communicate AB plc with a siemens one. I actually get them communicate with each other but I have a question about swapping.

For example, when sending a dint value(temperature etc) to siemens plc, I need to swap it but there are also dword values which I created bool by bool (start,stop, etc) but they are sent as dword to siemens side. When sending this dword value it is not needed to swap.I didnt understand the reason of this. Dont they recorded memory in same manner ? Why they both dont need swap ?

Thanks in advance.

 

[sigmadelta]

Keep this in mind (using double word address MD 0 as an example):

MD 0 consists of 4 bytes: MB 0, MB 1, MB 2 & MB 3

Byte MB 0 is the most significant and MB 3 is the least

Within the byte MB 0, bit M 0.7 is the most significant, and M 0.0 is the least.

So in the whole double word MD 0, M 0.7 is the highest bit and M 3.0 is the lowest.

Hope that helps.