CPU 315 DP analog addressing

[ahargrave]

I apologize if I've missed an existing thread on this topic. I have added a siemens rack to replace a Beckhoff remote IO rack and all is well except the analog card (331-7HF01-0AB0)

The Beckhoff addressing:
CH 0-1 PIB320 ,
CH 2-3 PIB323 ,
CH 4-5 PIB326 ,
CH 6-7 PIB329

Siemens card will only allow me to enter starting address as 320.Im fairly new to Siemens and could use some help with this issue. My question is: Can this module be wired to have these addresses be active or do I need to readdress these in project.

attached is a copy of current wiring.

CH 0-1 & CH 2-3 2wire (D)
CH 4-5 & CH 6-7 4wire (C)

Thank you for any help

 

[JRW]

You will have to re address
PIW320 is bytes 320/321
PIW322 is bytes 322/323
and so on
You get the picture
A PIW is 2 bytes but it will be in order

 

[mk42]

You will have to re address
PIW320 is bytes 320/321
PIW322 is bytes 322/323
and so on
You get the picture
A PIW is 2 bytes but it will be in order

W means word, in case that wasn't obvious. PID would be a Double word (4 bytes), PIB would be byte.

 

[JRW]

MK
You might as well explain analog scaling while your at it

 

[ahargrave]

Not necessary to explain AI Scaling.
It was just the difference in addressing from Byte to word i was having an issue with.

I guess my question is:
Can i force Siemens to use PIB instead of PIW ?

IE:
321 -323
326 - 329 ....etc.

 

[JRW]

Your analog values are going to be from 0-27648...
thats 0-10vdc, 4-20ma etc
Whats in your plc code?
It uses PIB?

 

[ahargrave]

....

Project is using PIB, but AI card will only let me enter start address ?
doesn't give me any options that i can locate.

 

[JRW]

Thats correct

Something doesnt add up with the Beckhoff
They cant just be using PIB because there is no resolution in that

 

[ahargrave]

I thought so as well, but i get no data on last two channels. ill check wiring
looks like the plc is using 3 bytes per channel

( PIB 320 - 322, PIB 323 - 325, PIB 326 - 328 & PIB 329 - 331 )

then later

PIW 321
PIW 324
PIW 327
PIW 330

This is odd to me or am i reading these wrong ? Data.jpg

 

[ahargrave]

I thought so as well, but i get no data on last two channels. ill check wiring
looks like the plc is using 3 bytes per channel

( PIB 320 - 322, PIB 323 - 325, PIB 326 - 328 & PIB 329 - 331 )

then later

PIW 321
PIW 324
PIW 327
PIW 330

This is odd to me or am i reading these wrong ? Data.jpg

do I change AI card addresses to start at PIW 321 ?

 

[JRW]

Since they won’t line up anyway,
I don’t think it matters
Most people start with even numbers

 

[mk42]

I thought so as well, but i get no data on last two channels. ill check wiring
looks like the plc is using 3 bytes per channel

( PIB 320 - 322, PIB 323 - 325, PIB 326 - 328 & PIB 329 - 331 )

then later

PIW 321
PIW 324
PIW 327
PIW 330

This is odd to me or am i reading these wrong ? Data.jpg

Each analog Channel should be two bytes (1 word). Channel 0 = 320-321, Channel 1 = 322-323, Channel 2 = 324-325, etc. I've never seen a 3 byte setup like your program has, but it definitely isn't how the Siemens modules work. You pick the start address for the first channel, and the other channels increment from there.

Also, why are you grouping the channels in pairs for the tags? Each channel has two bytes of data.

Possible idea: Did the previous module pack two analog channels into 3 bytes (12 bit resolution)? That's the only thing I can think of that makes any sense....

 

[L D[AR2P#0.0]]

Reading the Beckhoff documentation shows that some modules have a 3 bytes allocated per channel. The single byte is used for control/status and the other two bytes contain the analogue value, the scaling of which appears to be +/-32767 (although it also appears that the control byte can be used to change the scaling).


As already stated, there is no control/status byte for the Siemens analogue inputs and the scaling is +/-27648



Given that you are replacing the Beckhoff with Siemens, you need to understand what is being done with the control/status bytes and the scaling so you can provide the same functionality.


Post a cut down version of your project with the blocks that process the analogue inputs for further assistance.

 

[ahargrave]

PIB is used in SL
PIW in LAD

 

[ahargrave]

Additional rungs

BTW
I should add that i did not write this program. nor do i speak German. Lol