talking between S7314 and S7 318 CPU

I was wondering if somebody could give me ahead start on how i would send a bit from one plc to another.For example, when an input is on in a 314cpu, i want the 318cpu to see this. I would like to do this through an MPI network. I have already netwroked these two plcs. To i need to send this via a DB. Cansomeone send me some simple code and instructions on how to do this. thanks in advance

Never done it but try here, usually lots of examples here as well



http://support.automation.siemens.com/WW/llisapi.dll?query=Ethernet+S7-300+S7-200&func=cslib.cssearch&content=skm%2Fmain.asp&lang=en&siteid=cseus&objaction=cssearch&searchinprim=0&nodeid0=4000024&x=25&y=6

aussiesurf

I think that the simplest way to do this is with an unconfigured connection. You can use SF68 (X_PUT) and SFC 67 (X_GET) to achieve what you want, as they are 'PUT' and 'GET', the blocks only need to be in one of the PLC's not both.

Let's use SFC68 for the example, the 314 MPI address is 2 and the 318 MPI address is 3, the data to be 'put' from the 314 to the 318 is in DB1 and is the first 8 bytes, this needs to be placed in the 318 in DB10....

I will just outline the important pins on SFC68

DEST_ID - 16#3
VAR_ADDR - P#DB10.DBX0.0 BYTE 8
SD - P#DB1.DBX0.0 BYTE 8


The DEST_ID pin is the MPI address of the 'partner' CPU in HEX
The VAR_ADDR pin is the area that the data is to be placed in the partner CPU

The SD pin is the area on 'this' CPU where the data to put 'PUT' is stored, as you said you want to do this via a DB, I have used DB addresses in this example, if you wish to use Input bytes, then change the SD pin to point to the input bytes you want, for example to put input byte 1 in the 318, on the SD pin write P#I0.0 byte 1, remember the destination address should be the same length as the data being sent, so in this case you would need to have P#DB10.DBX0.0 BYTE 1 on the VAR_ADDR pin.

Paul

thanks paul, makes sense. what i dont get though is you said i need to use both sf68 and sf 67 yet you only mention instructions for sf67. do i need to use sf 68 at all?

you only need to use SFC68 (X_GET) if you wish to 'get' data out of the 318, the pins on SFC68 are similar to SFC67, if you want some assistance with this one, I will post an example

Paul

Since you've already decided on the MPI network as the media and you only want to transfer a bit why not use the S7 Global Data?
It's very neat and easy and needs no programming.

The configuration editor is like a spreadsheet. The columns represent the PLCs in your project (in this case you'll only need two columns) and the rows represent the packets of data to be sent between the CPUs. You can specify, for example, M20.1 from CPU1 to be sent continuously to DB14.DBX17.2 in CPU2. Or 6 double-words starting at DB12.DBB0 from CPU2 to be sent continuously to MB100 onwards at CPU1. You just fill in what you want, download it to both CPUs and off they go. The Global Data editor is a part of the MPI Network configuration at the Project level in STEP7.

As in the rest of life there's no such thing as a free lunch. Global Data transfer has limitations to the amount of memory you can transfer and the number of CPUs which can participate. It's an MPI-only feature (no Profibus or Ethernet). I think the Global Data transfer is regarded as a low-priority task in the CPU so if anything more pressing comes along you will find it is not deterministic. Try it and see - it may still fit what you want here.

Regards

Ken