Calculate the maximum number of devices connected to a single PLC

dchartier

Hello Matrex;

I found the link to your document here:

https://www.dmcinfo.com/latest-thinking/blog/id/3403/the-basics-of-siemens-s7-plc-io-addressing

Hope this helps,

Daniel Chartier

 Hi, 

If I want to use a device which has about 1400 bytes of data in each packet, how can I calculate the maximum number of devices I can connect to a single PLC? Lets say the 1518 IO Process Image is 32kBytes, does that mean I can only have 32000/1400 ~ 22 number of devices? 

Is there a way to expand this number? Is it possible to request process IO within multiple scans? 
I have control over the sampling frequency. It's quite low: 1-10Hz. 

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Split from Process Image.

PreLC

 Hi, 

If I want to use a device which has about 1400 bytes of data in each packet, how can I calculate the maximum number of devices I can connect to a single PLC? Lets say the 1518 IO Process Image is 32kBytes, does that mean I can only have 32000/1400 ~ 22 number of devices? 

Is there a way to expand this number? Is it possible to request process IO within multiple scans? 
I have control over the sampling frequency. It's quite low: 1-10Hz.

 The PLC's data sheet has the limit you can work with. There is also the maximum amount of I/O device connections that PLC can have.

Hi Hati, Thanks for your response.

I tried to check that: CPU 1518-4 PN/DP MFP Product Information

Could you please clarify how to calculate the number of IO that can be connected as a function of process image and  data-size per IO?
Lets say, 1400Bytes input per device: How many devices can I connect to CPU 1518-4 PN/DP?

Also, it also mentions 8kb per CP: Does that mean adding a CP adds 8kb of IO Image?

Hati

 

PreLC

 Hi, 

If I want to use a device which has about 1400 bytes of data in each packet, how can I calculate the maximum number of devices I can connect to a single PLC? Lets say the 1518 IO Process Image is 32kBytes, does that mean I can only have 32000/1400 ~ 22 number of devices? 

Is there a way to expand this number? Is it possible to request process IO within multiple scans? 
I have control over the sampling frequency. It's quite low: 1-10Hz.

 The PLC's data sheet has the limit you can work with. There is also the maximum amount of I/O device connections that PLC can have.

PreLC

 

Hi Hati, Thanks for your response.

I tried to check that: https://mall.industry.siemens.com/mall/en/WW/Catalog/Products/10341015?activeTab=productinformation&regionUrl=WW#:~:text=16%C2%A0384%3B%20max.%20number%20of%20modules%20/%20submodules

Could you please clarify how to calculate the number of IO that can be connected as a function of process image and  data-size per IO?
Lets say, 1400Bytes input per device: How many devices can I connect to CPU 1518-4 PN/DP?

Also, it also mentions 8kb per CP: Does that mean adding a CP adds 8kb of IO Image?

Hati

 

PreLC

 Hi, 

If I want to use a device which has about 1400 bytes of data in each packet, how can I calculate the maximum number of devices I can connect to a single PLC? Lets say the 1518 IO Process Image is 32kBytes, does that mean I can only have 32000/1400 ~ 22 number of devices? 

Is there a way to expand this number? Is it possible to request process IO within multiple scans? 
I have control over the sampling frequency. It's quite low: 1-10Hz.

 The PLC's data sheet has the limit you can work with. There is also the maximum amount of I/O device connections that PLC can have.

 

 If you look at the Datasheet, you can see that the first interface (X1) Supports the connection of 512 IO devices . Interface 2 (X2) supports the connection of 128 IO devices. And Profibus supports 125 IO device connections.

The Process image size of the processor  is 32kbytes. Adding CP cards, doesn't increase the size of the process image.

There is the Maximum each interface can handle. Interface 2 can only handle 8kbytes and Interface 1 can handle 32kbytes.