MODBUS RTU s7-1200 and Et200s software difference

naturephoenix

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Hey ,
Can someone explain me what's programming difference in realisation of the modbus rtu regarding these 2 CPUs.
I have worked with s7-1200 and with CM in your program you just need in a case of modbus master to use 2 functions. One function you use once in OB100 and another you are using cyclic in OB1
First function is Mb_comm_load(OB100)
Second function is mb_master_fb (OB1).
I dont need to take care of the modbus protocol rules with s7-1200 modbus rtu solution.

My question is how this going with ET200s side cuz friend of mine told me here we have to deal with construction of MODBUS message. IS that true?
So with Et200s CPU and 6ES7-138-4DF11-0AB0 there are function S_SEND and S_RECEIVE.
Should I take care for modbus message rules? COnstantly send requests with S_SEND to 6ES7-138-4DF11-0AB0 and constantly listen incoming bytes with S_RECEIVE from 6ES7-138-4DF11-0AB0.
Or basically all has been resolved on its easy way with those two functions same as it is case with s7-1200 and CM RTU 485 module
 
I have checked functions FB2 and FB3 on the Et200s side, I havent found input parameter modbus register startibg address. This parameter is present in master function in s7-1200
 
with et200s it is totally different than with 1200 or ET200SP if you are making MB master to ET200s.

On 200s you need to contruct message (offset, how many bytes, lenght.) Also you need to send query and then listen certain time with listening block, if you get reply.
It can be done, but not as easy as on 1200 or ET200SP series.

But if you do only MB slave, then it isn't so hard. For slave configuration is more like on 300CPU with 300 series serial card.

(ET200SP IO's can also connected to ET200S as remote IO)
 
with et200s it is totally different than with 1200 or ET200SP if you are making MB master to ET200s.

On 200s you need to contruct message (offset, how many bytes, lenght.) Also you need to send query and then listen certain time with listening block, if you get reply.
It can be done, but not as easy as on 1200 or ET200SP series.

But if you do only MB slave, then it isn't so hard. For slave configuration is more like on 300CPU with 300 series serial card.

(ET200SP IO's can also connected to ET200S as remote IO)

Thx for clarificTion.

Any examples beside siemens example between s7-300 master and et200s as slave?
 
You can look 1SI examples, there is some
https://support.industry.siemens.co...n=ps&o=DefaultRankingDesc&pnid=14089&lc=en-WW

This is from memory, but if you load Siemens blocks for ET200s, there should be examples on step7 library folder after installation
1SI_Disk1_V253.ZIP )

https://support.industry.siemens.co...he-serial-interface-et200s-1si?dti=0&lc=en-CR

Then there is couple manuals where communication method is descripted

ET 200S Serial Interface Modbus/USS Module User Manual

https://cache.industry.siemens.com/dl/files/658/9127658/att_52060/v1/modbus_y_uss1_76.pdf

and

ET 200S
Serial interface modules

http://public.eandm.com/Public_Docs/et200s_serial_interface.pdf


page 25 and 134 have timing diagram. If you enable your blocks according that timing, you should get response from slave.

You can put both blocks (send/recv) inside one own FB-block.
Then make for every different modbus request different FB and instance DB.
Enable only one block at time with counter and change request if reply or timeout.




p.s Easiest route could be use ET200s CPU, but instead of ET200s own modbus card use ET200SP modbus card with IM-interface module (Profinet).
That way you have working code allready from your 1200 CPU. ET200SP IM and modbus card cost little bit more, but you save lot of time on programming and testing.
 
Last edited:
You can look 1SI examples, there is some
https://support.industry.siemens.co...n=ps&o=DefaultRankingDesc&pnid=14089&lc=en-WW

This is from memory, but if you load Siemens blocks for ET200s, there should be examples on step7 library folder after installation
1SI_Disk1_V253.ZIP )

https://support.industry.siemens.co...he-serial-interface-et200s-1si?dti=0&lc=en-CR

Then there is couple manuals where communication method is descripted

ET 200S Serial Interface Modbus/USS Module User Manual

https://cache.industry.siemens.com/dl/files/658/9127658/att_52060/v1/modbus_y_uss1_76.pdf

and

ET 200S
Serial interface modules

http://public.eandm.com/Public_Docs/et200s_serial_interface.pdf


page 25 and 134 have timing diagram. If you enable your blocks according that timing, you should get response from slave.

You can put both blocks (send/recv) inside one own FB-block.
Then make for every different modbus request different FB and instance DB.
Enable only one block at time with counter and change request if reply or timeout.




p.s Easiest route could be use ET200s CPU, but instead of ET200s own modbus card use ET200SP modbus card with IM-interface module (Profinet).
That way you have working code allready from your 1200 CPU. ET200SP IM and modbus card cost little bit more, but you save lot of time on programming and testing.

Thx a lot will takedetailed look and let u know after.
Just to clarify for ur latest proporsal:
Can the IM be
6Es7 151-3AA23 - 0AB0
This is interface moduke profinet i have used with et200s. Can iput modbus card on it from er200sp family?
 
Thx a lot will takedetailed look and let u know after.
Just to clarify for ur latest proporsal:
Can the IM be
6Es7 151-3AA23 - 0AB0
This is interface moduke profinet i have used with et200s. Can iput modbus card on it from er200sp family?


No, ET200SP have different card bases and dimensions

http://w3.siemens.com/mcms/distribu...et-200sp/interface-modules/pages/default.aspx

You need one from 155-6Axxxx interface module series, ET200SP PtP card and power feeding (White) card base for PtP-card (6ES7193-6BP00-0DA0). If you only use one card, then basic unit is good enought.
Of course you can also add different cards from 200SP series to this remote rack.

p.s Assumed that you used profinet, Interface module can also be profibus, on that case 6ES7155-6BA00-0CN0
 
Last edited:

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