RhodyCho

Alright, so I'm a bit confused. I have been under the impression that once the key switch is placed in Program, all ladder execution ceases and outputs are frozen (selectable under the I/O Module Configuration). I was going through a program for a L61 that has roughly a dozen periodic tasks with ladder routines under them. When the controller is placed in Program there are at least a couple routines that run, as a GSV for Controller Status is performed and then in another routine an alarm tag bit is set to notify users the key switch is not in run. I've looked under Controller Properties and the properties for individual tasks but don't see anything involving a 'run when in Program mode' selection. What am I missing here?

A PID would be used if you're planning on controlling something, such as flow into the tanks or level of the tanks, with a control valve or variable speed drive (pump). If that's not the case, then no, a PID would not be useful. Are you pumping into these tanks or gravity fed? Also, for future ref, you don't necessarily have to drill into tanks for level information. Depending on what kind of tanks they are, i.e what material, open or closed top, etc. and whether you need point level, as in a high/low level switches, or continuous level, as in a constant level measurement (in feet, inches, % full, etc), there may be other options.

Is this for troubleshooting or will it be a routine action?

Hi Nizam, Just a question or two out of curiousity here - in terms of Yokogawa, I've only had experience with one of their small DIN-rail mountable controllers; is the process of setting up the RTU interface on their DCS simple? Is there an add-on module that you had to obtain for that? I'm assuming the DCS will be the 'master' device.

Yes, that custom instruction is working. I ended up modifying it somewhat but my hats off to you for clever ladder design. Appreciate the input on this one. The solution is basically a series of copy, swap, and copy instructions for those interested. I believe the original HW serial interface was set up to communicate with the older PLC 5 and SLC 500 series so perhaps their string configuration was different? You basically have to map your tag to a file number and '9' is the designated string number. I thought I recall that file 9 however was an integer file by default in the last SLC 5/05 I saw.

Thanks for the replies. The problem with that swap byte instruction is that it is only applicable to INT, DINT, and Reals (note that SINT values are not included). The way the instruction help is shown using the letters, I feel, is actually somewhat misleading. I can swap some DINT values around and then change the DINT tag's "Style" under the tag browser to ASCII and see lettering but this does not mean I can view the tag as a string value, on an HMI for example. It would only show up as the numbers. I believe y2k's suggestion may work, although I'm having some issues with it upon first trial. When copying an INT value after performing a byte swap into a String's Data element, the characters are again rearranged probably because the string's data elements are of the SINT type; I'll keep trying may be. The amount of instructions this may require is probably more than I want to add for this one application so I may just send a number corresponding to one of say 20 different string values and then translate it on the HMI with a multi-state indicator.

Hello Again, I'm sending some string data serially from a Honeywell Serial Interface module to an AB CL 5561 controller using port 0 set in the "system" mode which is set for DF1 Point to Point. When I send a value, say "ABCDEFGH" from the Honeywell system, I get a "CDAB" in my string tag's .LEN value (if I change its style to ASCII from decimal) and a "FEHG" in the first four elements of the strings .DATA value. So the actual string's value appears as 'FEHG...' Ultimately I'm wanting to view the correct string on a PanelView. I've tried a byte swap instruction but that only works for integer or real values but I can swap the LEN characters around so they are in the proper order. The problem then is how do I view them as ASCII characters and not their decimal equivalents. The Integer to String instructions only seem to work for numbers, or am I wrong there? I thought I could display each character individually on the PV application in the order required to make the combination appear as the original string but the values from the individual DATA elements only appear as the decimal number. Any thoughts on how I could rearrange my strings? Thanks.

Good info, thanks.

Hey guys, Have a 1756 CL rack with the EN2T Ethernet module with a program written by the vendor. For some odd reason, the module doesn't show up on the I/O Config folder. The file numbers skip position [1] which is the module. I can get online with it no problems however so there is no real issue other than it seeming odd. I have not tried the Discover Modules option. Thoughts?

Thanks for the responses, good stuff. I'm a bit upset at myself for not thinking of that divide method. Think I'll have a few beers for atonement.

Hi, using RSLogix500 on some ML1400's. I'm interested in looking at the second half of a 16 bit word. Actually I want to shift bits 8-15 of say N7:0 to another integer word, say N7:1 bits 0-7. I have to do this for a number of words so doing it bitwise is a bit of a hassle. Any suggestions would be appreciated.

Thanks Mickey. Yeah I did have the Lite version but just received the OEM version and loaded it up. Have a basic DDE going on, pulling in three values. It looks like I can go through some of those examples you linked and learn a few things. Hoping to pull in 27 data points with a time stamp in a defined interval, say every minute. Thanks.

Good morning folks. I'm relatively new to the PLC world, only been dealing with them the last year or so. I'm interested in pulling data out of a ML1400 into an Excel sheet on a PC, either connected directly through ethernet or through a cellular modem. Ideally I would use this Excel sheet to actually log the data, in other words bring in the data every 5 or 10 seconds along with a time stamp, and populate the sheet for a day or more. I have a combination of integers, floating points, and bits I'm needing to pull in. I've established a DDE and assigned a topic to the processor but I'm a bit confused on what to do from there. Can someone provide some pointers or a link to a prior post where this was covered? I would certainly appreciate it. I did do some searching but did not find anything specific. I'm using RS Linx Classic Lite and I have several integers in the processor representing time (hours, minutes, seconds) feeding from a Panelview. Thanks.