Step 5 : P and Q area

Hello,

For our final project we need to use a STEP5 (115U CPU943B) PLC that is connected to PROFIBUS with an IM308C.

Everything works fine, but there is something we don't understand. For the adressing you can choose linear addressing, Page addressing and DP window.

We understand that Page adressing and DP window is only nescessary if you have a lot of perifery addresses.

But, in linear en and in Page addressing you can choose for Parea and Qarea or Ppage and Qpage. I did a lot of research but didn't find out a good definition for that P and Q. I believe te P is the normal I/O area, but wath does that Q stands for?

Is it the same like in STEP 7 , OB 1 and PIP proces area? or is it something completly different?

Explanation of OB1 and PIP :
https://support.automation.siemens....objaction=csview&extranet=standard&viewreg=WW

Thanks in advance.

Mathias Deneire

I = Input Image
Q = Output Image
P = Periphery (real IO)

In Step 7 there is PI and PQ, in step 5 there was just P, you knew the difference by the instuction, i.e. L PY5 is loading inputs (Byte 5 equivalent to updating Input Byte 5), T PY5 is transferring to outputs (Byte 5 equivalent to updating Output Byte 5).

PeterW said:

I = Input Image
Q = Output Image
P = Periphery (real IO)

In Step 7 there is PI and PQ, in step 5 there was just P, you knew the difference by the instuction, i.e. L PY5 is loading inputs (Byte 5 equivalent to updating Input Byte 5), T PY5 is transferring to outputs (Byte 5 equivalent to updating Output Byte 5).

Click to expand...

tnks for responding,

but i think i've been misunderstood.
I know you have the normal in and outputs I/O and the perhery.and I also know aboud the load and transfer but when you look in the manual for the 115U cpu you find that input output area is subdevided in several parts.

- F000(H) I/O modules (Parea) 60kB
- F100(H) Q area 60,25kB

So my question is what is that Q area? I don't know if it was that wath you where explaining?

thanks a lot

That's the absolute memory area where the Q image is stored.

PeterW said:

That's the absolute memory area where the Q image is stored.

Click to expand...

and is that Q image the place where al outputs are stored? or what is it exactly?

Because the P area is the same like I/O modulles?

I- and Q- works with the input- and output-image, they are updated once every scan.

PII or 'process image inputs' is the state of the inputcard at the beginning of the scan. They stay the same during the duration of the scan.

PIQ or 'Process image outputs' is the state of the outputs during the execution of the program. This information is copied to the outputcards at the end of the scan or cyclus.

With 'L/T Px.y' you work directly with the actual state of the hardwired I/O without waiting for the beginning or end of the scan.

ivo.maenen said:

I- and Q- works with the input- and output-image, they are updated once every scan.

PII or 'process image inputs' is the state of the inputcard at the beginning of the scan. They stay the same during the duration of the scan.

PIQ or 'Process image outputs' is the state of the outputs during the execution of the program. This information is copied to the outputcards at the end of the scan or cyclus.

With 'L/T Px.y' you work directly with the actual state of the hardwired I/O without waiting for the beginning or end of the scan.

Click to expand...

Yeah, i know,

but, wath is the link now with linear addressing with P area and Q area? or Ppage programming or Q page programming?

thats wath i don't get.

Thanks a lot for the responses

The P area is only 256 bytes in S5; this is your normal I/O area. To be able to expand the amount of I/O beyond 256 you also have a Q area to use; this exists in addition to the P area.

From memory, there are some restrictions on how this is used. You cannot duplicate addresses in the Q area like you can in the P area; so each address is either an input or an output but not both (I think).

Posible instructions for Load:

L IW 0 - load word 0 from the Input process image (P area)
L PY 0 - Load input word 0 directly from the periphery (P area)
L OW 0 - Load word 0 from the Q area

Posible instructions for Transfer:

T QW 0 - Transfer to Output Word 0 of the process image (P area)
T PY 0 - Transfer directly to Output word 0 in the periphery (P area)
T OW 0 - Transfer to word 0 in the Q area

I recently had to re-write the Siemens S5 HMI driver for the MP277 to work in the Q area because there wasn't sufficient address space free in the P Area.

I hope that this is useful to you.

Nick

Manglemender

Q = Output Image, its not an expansion to the P area, its an image of the output P area taken between scans. Just as the I (Input Image) is an image of the input P area taken between scans.

El_neire said:

Hello,

For our final project we need to use a STEP5 (115U CPU943B) PLC that is connected to PROFIBUS with an IM308C.

Everything works fine, but there is something we don't understand. For the adressing you can choose linear addressing, Page addressing and DP window.

We understand that Page adressing and DP window is only nescessary if you have a lot of perifery addresses.

But, in linear en and in Page addressing you can choose for Parea and Qarea or Ppage and Qpage. I did a lot of research but didn't find out a good definition for that P and Q. I believe te P is the normal I/O area, but wath does that Q stands for?

Is it the same like in STEP 7 , OB 1 and PIP proces area? or is it something completly different?

Explanation of OB1 and PIP :
https://support.automation.siemens....objaction=csview&extranet=standard&viewreg=WW

Thanks in advance.

Mathias Deneire

Click to expand...

OK, I have looked at the ET200 manual http://support.automation.siemens.com/WW/llisapi.dll?query=Ppage+and+Qpage&func=cslib.cssearch&content=adsearch%2Fadsearch.aspx〈=en&siteid=cseus&objaction=cssearch&searchinprim=0&nodeid0=10805082&x=23&y=7

Section 6.1 deals with addressing.

Linear addressing is using the periphery data area (I and Q) directly, this is limited to the 256 bytes in each direction (PY0 to PY255). The transfer of data is fast and direct.

Page addressing is using a block of the periphery area in both the I and Q periphery area, PY192 to PY254 (63 bytes in total). PY255 is the page address, you can have 16 pages (1008 bytes) per DP link and 8 links (to different field devices) in total, which means a total of 16*8=256 pages in total.

The transfer of data is slower as only 1 page of the 256 can be accessed at a time (in each direction of data flow).

Reading the manual, it states you set the page ID first (PY255 for example set to 12, now both I Perphery area (inputs) and Q periphery area (outputs) are set to page 12, which means 1 page of 1 DP slave is accessed. Now the data can be written to and/or read from. During this period you should be transferring data from pre conditioned data blcok areas or flag areas to the Q periphery and transferring from the I periphery to your read data block area or flag area.

There is also the DP window method which utilises the standard FB92.

You cannot mix and match.

The address range it enters, such as the Input Periphery F000 to F0FF are the HEX absolute addresses in memory where the periphery exists. This is to aid in programming, as most would want to use block transfers to move data about.

PeterW said:

Manglemender

Q = Output Image, its not an expansion to the P area, its an image of the output P area taken between scans. Just as the I (Input Image) is an image of the input P area taken between scans.

Click to expand...

Peter,

The "Q area" is quite seperate from the Q process image and is referenced as OW xxx

Nick

So the Q area is just an addition.

PeterW, thanks for the responses. I'm greatfull for your effort!!. But if you look at table 6-2 on page 131 you can see that P area and Q area both have Input and output. So Q area is, correct me if i'm wrong, not only Output image, but just like nick says more an additionele.

Everyone thanks for the responses, seems to be that i was looking for a to difficult explanation