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regarding master slave configuration between two 313c-2dp
Created by: deepak.samal05 at: 11/29/2009 3:10 AM (5 Replies)
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| 12/5/2009 9:55 PM | |
Joined: 9/27/2006 Last visit: 1/24/2025 Posts: 12330 Rating:
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Hello deepak; In another thread I pointed out a Siemens FAQ that showed how to connect 2 S7 PLCs as masrter and slave over Profibus-DP. Here is the link once again, just in case you missed it: http://support.automation.siemens.com/WW/view/en/6518822 Now, it seems that what is confusing you is the data exchange addressing between the master and the slave, am I correct? Look at point 5 in the FAQ, defining the input-output areas, both for the slave and the master; compare both. Profibus-DP was originally designed to transfer small elements of data at hign speed between an intelligent master and a "dumb" slave, that is one whose data exchange area was configured through the gsd file. With an "intelligent" slave (another CPU, for example), then you have to configure the exchange ares though the input/output addresses, that is I and Q addresses. Note that the example shows E and A addreses that correspond to German mnemonics. So, first determine what amount of data you want to exchange between the 2 CPUs, and configure them line per line in the Configuration tab; then transfer to that address the data you want to send to the other partner. Hope this helps clear things up, Daniel Chartier |
| 12/6/2009 2:59 AM | |
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Joined: 9/27/2006 Last visit: 1/24/2025 Posts: 12330 Rating:
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Hello deepak; If you are using CPUs 313C-2DP, then addresses I124.x and Q124.x are reserved for your integrated I/Os. So you cannot assign them for your DP exchange areas. Please open your cross-reference and select I and Q byte or word addresses that are not used in your configuration or your program. Al;so, you cannot transfer directly Mxxx or DByy.DBWzz addresses directly over Profibus-DP. Once you know how many words (or bytes) you need to transfer between the master and the slave, and once you have prepared the data exchange areas to cover ythe amount of data to be transfered, you use MOV instructions to place the data from the DByy,DBWzz addresses to the I or Q addreses reserved for Profibus. One more point: when to use I or Q addresses? Well from the master's point of view, anything that is written to a slave is considered an output, and uses Q addresses; anything that is read from the slave is an input, and uses I addresses. From the slaves's point of view, whatever is written to the master is an output, whatever comes from the master is an input. So be careful: if you configure in the master's configuration 4 words IN and 8 words OUT, you must check that the slaveès configuration is reversed: 8 words IN, 4 words OUT. This is critical and will cause a SF on both the master and slave if it is not respected. Also, have a look at the PowwerPoint presentation prepared by Vivek (aka Eastern) in this previousexchange. It might give you some pointers: /tf/WW/en/Posts/27465 Hope this helps, Daniel Chartier |
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