Cominbing two 16 bits to get a 32 bit

[Jamie123]

Hello,
I'm currently trying to read an encoder value from a drive via ModBus. The encoder value is split into higher 16 bit and lower 16 bit, hence I have to read two registers.

Is there an easy way to combine the two values to get the single 32 bit value I'm after?

TIA

 

Jamie

[ORSO2001]

Hi,

for example...you have 2 variables Uint16 (A = higher, B = lower) and 1 variable Uint32 (C)... you have to multiply the A for 65536 and store the result in C...after you have to add B in C.

I think that also you can use some buffer functions...but with first only 2 actions are needed.

[Saragani]

You can also just put a 32 bit tag in your modbus operation, and the PLC will read 2 registers instead, (if you give it address 0, then it will read both 0 and 1).

Then, assuming that order of the high and low on the encoder (the endianess of the numbers) is the same as in the PLC, then it would work fine (if not, them the high and low 16 bits numbers will be flipped, and then you could better have to read them separately, and do what ORSO suggested)

[Saragani]

Anyway with buffers it's 3 actions:

Copy tag to buffer: From low, offset 0 to buffer

Copy tag to buffer: From high, offset 2 to buffer

Copy buffer to tag: From buffer, offset 0, length 4, to Int32 or UInt32

[Jamie123]

Thanks for the replies. ORSO2001's method worked fine1.