SLC Immediate Output


Thread Starter

Anthony Kerstens

I have a 5/04 with and SN and Flex I/O Outputs. Are there any problems with using the IOM instruction with Flex I/O? (Yes, I know a module in the SLC rack would be faster than the Flex, but the architecture is not mine and cannot be changed.) Anthony Kerstens P.Eng.

Michel A. Levesque, eng.

> I have a 5/04 with and SN and Flex I/O Outputs. > > Are there any problems with using the IOM instruction with Flex I/O? Yes, you could have problems with this. The only that an IOM works with FLex I/O on a SN is to use direct mapping of I/O' other words no pseudo-block transfers (or in the newest firmwares, no BTR,BTW isntructions). This is the same restriction as in a PLC. An IOM will send data to the I/O table, but if a block transfer is used this delays the update, thus defeating the original purpose of an IOM. The problem is in the SN (with it's enherent mapping) and not the in Flex I/O's themselves.

Eric M. Klintworth

The immediate in and out instructions don't really work with the SN. They can apparently be programmed (it worked offline OK when I tried), but they would only get the data immediately to/from the SN, not to the I/O. You would still have to wait for the next Remote I/O scan before the data got to your outputs. So the IOM would be a little faster than waiting until the end of the program scan, but not nearly as fast it would be to a module in the SLC rack. To quote from the SN manual (1747-6.6): "The SLC processor scan and RIO scanner scan are independent (asynchronous) of each other. The SLC processor reads the scanner input image file during its input scan and writes the output image file to the scanner during its output scan. The RIO scanner continues reading inputs and writing outputs to the scanner I/O image file, independent of the SLC processor scan cycle." Oh, and be aware, the SN isn't especially straightforward to program if you haven't done it before. Its easier (but not easy) if you have experience with RI/O. Eric M. Klintworth, PE Sharp Technologies, Inc. Columbus, OH

Anthony Kerstens

Thanks. I guess I'm pretty well stuck with home run wiring to the main rack then. Now I just have to convince others to allow a variance in the design. :) Anthony Kerstens P.Eng.

Barb, Manufacturing Programmer, Hewlett-

We have a SLC with a RI/O (not exactly the same as what you have) and I use an IIM and an IOM on some of the RIO points with no problem. FWIW.