1771-IFE (Analog Input) Modules

[Bill Linne 0]

Where does the data "live" for these modules? When viewing the data table (in module setup), you are presented with the present data value (I know where that lives!) but you can insert the Raw Min and Raw Max values for each channel, too. Where do those values live? The reason I ask is because in one of my modules, the Raw Min and Raw Max values are not static - they are frequently changing. Which means, I think, that the buffers they are in are being overwritten by something else. Without knowing where the values are, I don't know how to isolate the offending instruction that is overwriting them. Any ideas? p.s. I sure hope that this is not so simple that I look like a dummy . . .

[OkiePC 14]

Look for a BTW instruction that is directed to the slot/module with the IFE. Those values in that block transfer from a data table are used to configure the input module. Usually the IFE is programmed with a BTW and a BTR that alternate. I'll attach a worsheet that contains all the comments for these addresses. It lets you enter the starting address from your BTW instruction, and can be saved as a .csv file and imported into RSLogix5. Don't do that, until you've checked out the usage of these addresses, you may not want to overwrite address comments specific to your machine. Some one may have used these addresses inadvertently, not realizing they were already in use. Hope this helps PC AB_1771_IFE_ADDRESS_COMMENTS.xls Edited 27 Jun 2005 by OkiePC

[Guest Guest]

OkiePC: I understand the BTR/BTW stuff okay. Once that is done, and you view the setup screen, you can see the Channel/Symbol/Description/Address/Type/Data/Voltage or Current/Raw Min/Raw Max in a table. The Data is obviously the value being read by the module. The two last columns, Raw Min and Raw Max look as though they would also be data in a database. My problem is that in this one case, that Raw Min & Raw Max data is dynamically changing and it shouldn't be. It should be static. If I knew where that data lives, I could figure out why and how it is being overwritten. I hope this is clearer.

[Bill Linne 0]

OkiePC (and others): The reply immediately above is mine. I forgot to log in before posting it. Sorry.

[OkiePC 14]

The raw min and raw max values are located in the data table from your BTW that goes to the IFE. Post the details in the BTW instruction, and I can tell you exactly which addresses to search on. The raw min value for CH1 should begin at the sixth address in the BTW, followed by the Raw Max value for CH1. After that it goes to channel two min then max, etc. Note that they are in BCD, so when viewing the data table, changing the radix to BCD will help you find them faster. In my excel workbook, the "Raw Min" value is commented as the MIN SCALE value.

[Bill Linne 0]

Okay, the BTW is at N14:0 and the BTR for the same module is at N14:10. The next module uses N14:20 & 30, respectively. When I view the N14 registers, only the first five words of each are other than zero. All words x5 thru x9 (05, 15, 25, etc) are zeros. Did I misunderstand something?

[Guest]

Greetings Bill, you’re not giving us ALL of the information about your BT’s ... but if the Data File (not the Control Block) begins at N14:0, then the chart below should help you find the addresses that you’re looking for ... the chart shows the "word assignments" that OkiePC was telling you about ... the chart is from page 4-8 of the 1771-IFE/C module’s User Manual ... the 1771-IFE/A or /B module’s layout should be close enough to work ... or see the comparable page in the appropriate User Manual ... if this doesn’t nail it down, please tell us ALL about your BTW settings ... and if all else fails, you might consider posting your .RSP file ... we'll be glad to take a look at it for you ... hope this helps and good luck ... and welcome to the forum ... Edited 27 Jun 2005 by Ron Beaufort

[OkiePC 14]

It sounds like your module is not using scaling in the BTW. In that case the BTW would be the minimum 5 words long. If the BTW length is greater than 10, you're overlapping the BTR, and will have serious problems. I have seen BTW lengths get changed accidently. If the length is 5, then the BTW doesn't send scaling info to the module, and it can be configured from the setup screen by typing in the correct values and hitting the accept edits button and then RSLogix will send a single BTW to the card. Also, you only need the BTW when power is first applied to the IFE card. After that, it can be disabled. There is a bit in the BTR that the card will set when it "needs" configuration data (brand new card). I use that bit in parallel with the PLC first scan bit to enable the BTW for IFEs. Often, programmers set them up to alternate with the BTR to guarantee that config data is written to the card in case that config bit fails to get turned on by the card. I have seen programmers write to the scaling values in PLC code. Usually this is done inconjunction with some sort of calibration procedure from an HMI, though and isn't something that dynamically changes. If you find that the length value is greater than 5 words for the BTW, try changing it to five and see if the problem goes away. Another possibility is that, even though you're not writing words 6-37, the RSLogix IFE setup screen may be using these addresses for display purposes. Probably not the case, though. Which channel(s) are giving you trouble? Are your actual outputs varying in response to what you see happening to the Raw Min and Raw Max values for that channel?

[Bill Linne 0]

Gents: I did misread the request for address, and furnished the control address for the BTW, not the data address. But I investigated the data address too, and found only one word of the the ten words to have a value in it. And that value did not match any of the valuse in the MIN/Max fields of the module. I may post a shortened version of the file tomorrow. I really appreciate the help, and I know that we'll get to the bottom of it eventually. Thanks again, Bill