This is probably true, but for better or worse, site practice here is to put all the ECBs in the STATION_ECB compound, so we can refer in IOM_ID to the letterbug only, and not have to use COMPOUND:ECB. Since we may scan blocks at intervals from BPC up to seconds, we scan the ECBs at BPC as well to avoid problems (though I don't personally have any 0.1-sec BPC applications; I don't know what people here do in that case). And Alex responded: "The CP60 will outperform in all respects CP40As if the I/O chain is split across multiple FCMs/DCMs." To achieve this, how much does one typically have to divide the legacy fieldbus across DCMs? Two 1x8's per DCM pair? One? The CP60s I have certainly seem capable of outperforming CP40As; the ones I have with 200-series I/O handle a pretty heavy IO load (including FBM224s) well. And others definitely outperform the CP30As I replaced (I used 1 FBI10E pair per two 1x8s). But in the one case I mentioned, the legacy fieldbus was split across 3 DCM pairs (not sure how many 1x8s total), and the idle time went down relative to the old CP40A. May be an isolated case, but checking the spreadsheet as Terry suggests is probably a good idea. Corey "Doucet, Terrence" <tdoucet@xxxxxxxxxxxxxxxxxx> Sent by: foxboro-bounce@xxxxxxxxxxxxx 10/21/2005 09:43 AM Please respond to foxboro To: foxboro cc: Subject: Re: [foxboro] CP60 and FBM legacy Troy, People should use the CP60 loading spreadsheet on the EDOC CD to perform their "what if" analysis. I suspect that this spreadsheet will show Jaime's CP60 fieldbus - overloaded. Although this thread started out as a loading question that has been answered by Alex, you now bring up a side issue that can affect systems. The best performance comes when FBM's (ECB's) run at the same scan rate = as the blocks. For example - FBM04 (mA) at 1.0 sec to AIN at 1.0 sec to = PID at 1.0 sec to AOUT at 1.0 sec back to FBM04 (could be different l'bug) with = ECB at 1 sec. You can phase the blocks if the basic processing cycle = (BPC)is 0.5 seconds and as long as you set the PRI correctly, all is OK. If you run your ECB's at 0.5 seconds in the above example, your 1 s AIN = will ignore half the mA input changes. On fast changing signals, this might get you in trouble. If the signal is not fast changing, then you could = be OK. You can run all at 0.5 sec but you need to carefully check loading. In any case, you never want to overload your CP. Regards, Terry _______________________________________________________________________ This mailing list is neither sponsored nor endorsed by Invensys Process Systems (formerly The Foxboro Company). Use the info you obtain here at your own risks. Read http://www.thecassandraproject.org/disclaimer.html foxboro mailing list: //www.freelists.org/list/foxboro to subscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=join to unsubscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=leave