Using output address as memory area ?

Hi every one

Since i am using modbus TCP to access my S7-1200 device

i need to write to coils in that plc , so instead of moving all the coil addresses 

to holding register db , i thought that why not make use of excess Q addresses (which are out of peripheral output area) as memory , is that gonna work fine ? ,

note when doing this , compilation gives only warnings,  no errors triggered

Related topic:How to map memory bits in process image output area 

Osama Awad

Hi every one

Since i am using modbus TCP to access my S7-1200 device

i need to write to coils in that plc , so instead of moving all the coil addresses 

to holding register db , i thought that why not make use of excess Q addresses (which are out of peripheral output area) as memory , is that gonna work fine ? ,

note when doing this , compilation gives only warnings,  no errors triggered

Your plan is a good one and should work. You need to test to make 100% sure.

There is something you can do about the warning also. Use the PEEK instruction available in the SCL coding language. This will give you the tool to read the output address indirectly.

That would mean you do not have to even register a PLC tag for the output area you are using. The PEEK instruction can then redirect the write-to-output Modbus/TCP action to whichever memory area you want.

Do note that if you "redirect" to a DB, that DB should not be optimized. The PEEK/POKE instructions only work on non-optimized memory areas.

Do these notes help you?

 Hello,

Osama Awad

Hi every one

Since i am using modbus TCP to access my S7-1200 device

i need to write to coils in that plc , so instead of moving all the coil addresses 

to holding register db , i thought that why not make use of excess Q addresses (which are out of peripheral output area) as memory , is that gonna work fine ? ,

note when doing this , compilation gives only warnings,  no errors triggered

 write to coils with MB TCP protocol is working without problems, you don't need use HR as work around. You have plenty of free places but all depends already used PI addresses so you need pay attention for overwrites errors. Basically you don't need to do any steps on your Server device, Client simply write via standard MB way and you'll have then values changed at your addresses, all do internal MB TCP driver automatically.

 Thank you Qwazee  ,, appreciate your response

qwazee

Related topic:How to map memory bits in process image output area 

Osama Awad

Hi every one

Since i am using modbus TCP to access my S7-1200 device

i need to write to coils in that plc , so instead of moving all the coil addresses 

to holding register db , i thought that why not make use of excess Q addresses (which are out of peripheral output area) as memory , is that gonna work fine ? ,

note when doing this , compilation gives only warnings,  no errors triggered

Your plan is a good one and should work. You need to test to make 100% sure.

There is something you can do about the warning also. Use the PEEK instruction available in the SCL coding language. This will give you the tool to read the output address indirectly.

That would mean you do not have to even register a PLC tag for the output area you are using. The PEEK instruction can then redirect the write-to-output Modbus/TCP action to whichever memory area you want.

Do note that if you "redirect" to a DB, that DB should not be optimized. The PEEK/POKE instructions only work on non-optimized memory areas.

Do these notes help you?

 Thank you Duris , that was so much helping

Duris_I

 Hello,

Osama Awad

Hi every one

Since i am using modbus TCP to access my S7-1200 device

i need to write to coils in that plc , so instead of moving all the coil addresses 

to holding register db , i thought that why not make use of excess Q addresses (which are out of peripheral output area) as memory , is that gonna work fine ? ,

note when doing this , compilation gives only warnings,  no errors triggered

 write to coils with MB TCP protocol is working without problems, you don't need use HR as work around. You have plenty of free places but all depends already used PI addresses so you need pay attention for overwrites errors. Basically you don't need to do any steps on your Server device, Client simply write via standard MB way and you'll have then values changed at your addresses, all do internal MB TCP driver automatically.