Siemens RTM instruction

kalabdel · May 27, 2020

Hello everyone,

Following a thread about hour meter I contacted Siemens tech support to finally ask a question I didn't have an answer to:
Where is there a limit on the number of Runtime counters for RTM instruction. The reply was ignorant, dismissive and flat out hostile. (I have been planning to switch away from siemens anyway)

Does anyone know why the limit?

sigmadelta · May 27, 2020

Which CPU model/part# do you have?

kalabdel · May 27, 2020

S7-1214C 6ES7214-1AG40-0XB0

I believe the limitation applies to all CPUs but I think the number (as in how many) differ.

Thanks

sigmadelta · May 27, 2020

This used to be stated in the technical specification of the S7-300 CPUs (ex: CPU 312C has only 1 runtime meter)... but I cannot for the life of me find it for the S7-1200.

The only thing I found so far is:

"The CPU operates up to 10 runtime hour meters to track the runtime hours of critical control
subsystems. You must start the individual hour meters with one RTM execution for each
timer. All runtime hour meters are stopped when the CPU makes a run-to-stop transition.
You can also stop individual timers with RTM execution mode 2."

Page 344:

https://cache.industry.siemens.com/...95681/v1/s71200_system_manual_en-US_en-US.pdf

JRW · May 27, 2020

So here's the scoop-
10 is the limit because that is all you have (at least with a 1200)

I started with 0 and went to 9- at 10 is the error

Below info- from the manual

NR Input

I, Q, M, D, L or constant
Number of the operating hours counter

Numbering starts with 0.

Parameter RET_VAL

Error code

(W#16#...)
Explanation

0000
No error

8080
Wrong number for the operating hours counter

8081
A negative value was passed to the PV parameter.

8082
Overflow of the operating hours counter

8091
The MODE input parameter contains an invalid value.

General error information
See also: Evaluating errors with GET_ERR_ID

kalabdel · May 27, 2020

Thanks gentlemen.

Why only 10? That was the reason I contacted tech support to have an understanding of why. Is it software or hardware limitation?
There limits on high speed counters, why? Because they rely on hardware and each CPU has different limits and hardware design.
There's limit on the number of block, why? Because there require memory and there finite amount of that?
Ett

janner_10 · May 27, 2020

Forget the limit - Just make your own - so much less fuss.

JRW · May 27, 2020

Tech support doesn't design them- just supports them

Ive told customers before "I dont answer why questions"

Appears to be what is put in the firmware

kalabdel · May 27, 2020

JRW said:
Tech support doesn't design them- just supports them

Ive told customers before "I dont answer why questions"

Appears to be what is put in the firmware

I would never ever say anything like that to a customer. I have way to much respect for them.

JRW · May 27, 2020

It was a joke.
You need a thicker skin too

kamenges · May 27, 2020

There is no reason for it. It was an arbitrary limit arrived at by the firmware developer probably because they have 10 fingers and couldn't see why anyone would need more than 10 instances. At least if they would have made the limit a multiple of 8 it would have felt better.

To JRW's point, Siemens (or Rockwell or Schneider or Omron, etc) are so big that the guys as the tech support level are so far separated from the development guys that there was zero hope of him being able to answer your question. Granted, just because his dog whizzed on the floor before he left for work today is no reason he shouldn't have replied professionally. But in the end you hit a guy with an unanswerable question on a bad day. It happens everywhere sometimes.

Keith

JRW · May 27, 2020

kamenges said:
There is no reason for it. It was an arbitrary limit arrived at by the firmware developer probably because they have 10 fingers and couldn't see why anyone would need more than 10 instances. At least if they would have made the limit a multiple of 8 it would have felt better.

Keith

I’m sure there is a good reason... accuracy, writing hours to mmc etc ...after 10 rtm’s

There’s a library with a run time block on the Siemens website for 1200/1500 For downloading

kalabdel · May 27, 2020

Thanks again everyone. I guess it is will remain a mystery for now.

kamenges · May 27, 2020

Originally posted by JRW:

I’m sure there is a good reason...

Well, when you find out what it is be sure to come back here and update this thread. Inquiring minds, you know. I just find it pretty hard to believe that a PLC family that is supposed to be able to run circles around Rockwell's best is so strapped for processing power or memory that it can't keep track of more than 10 time delta sums at a time. So if it wasn't for performance or memory reasons, what does that leave?

Keith

PLC · May 27, 2020

You guys sure are over analyzing this.
Why was 16 profinet devices picked for a max on a 1200?
You can go on forever...
It’s a system block (RTM), write your own Run time meter and go on your way

Siemens RTM instruction

kalabdel

Member

sigmadelta

Member

kalabdel

Member

sigmadelta

Member

JRW

Member

kalabdel

Member

janner_10

Lifetime Supporting Member

JRW

Member

kalabdel

Member

JRW

Member

kamenges

Member

JRW

Member

kalabdel

Member

kamenges

Member

PLC

Member

Similar Topics