Allen Bradley's ControlLogix and CompactLogix CPU processing speed

Can someone please tell me the CPU processing speed of ControlLogix L61 and CpmpactLogix L27ER??

That is an almost meaningless question. It depends not only on the processor selected, but also the firmware revision of the CPU, and the user program loaded. If you really MUST know, try googling "Instruction Execution Time ControlLogix L61". I don't have the time nor the patience to do simple searches for you.

Hi and welcome to the Forum...

Here is some Allen Bradley CPU info I posted recently. Perhaps some of it will answer your question.

There are links to Reference Manuals for instruction execution times and specs on CompactLogix and ControlLogix (L6x) CPUs...

CPU speed of Allen Bradley

Regards,
George

rdrast said:

That is an almost meaningless question. It depends not only on the processor selected, but also the firmware revision of the CPU, and the user program loaded. If you really MUST know, try googling "Instruction Execution Time ControlLogix L61". I don't have the time nor the patience to do simple searches for you.

Click to expand...

I do agree.
But, as with many of these questions, I say "What good does it do to know the answer?" If there is a quantifiable answer, when the dust clears, does it really make any difference? For example, is this a shoot out between one kind of PLC and another? If so, speed is the least important element of any such comparison. Perhaps this is a valuation question...as if to say that a "faster" PLC is somehow "better". ((If that were so, BTW, Keyance would have a much larger market share.))
An <<interesting>> question, but the answer, whatever it is, is not much use.

To Assume is to Presume...

To be frank, (Hi I'm Frank)

Without knowing the reason for the question, how can one say whether the question has meaning, or if the answer is of use?

I had a supervisor who recently came to me on a late shift and asked me to look at an issue on the floor.
I asked him something related to the issue and he asked me...

"What do you want to know that for?"

...in a somewhat smart tone. I then asked him...

"Why do you want to know why I want to know that?"

...He said...

"Sure it's a stupid question!"

...I replied...

"It may seem like a stupid question if you don't know the reason I asked it"

...He just walked off.

I went and solved the problem, after getting the answer to the question I'd asked from an operator. He later apologized.

While I do understand yere point of view, I think ye are being a little presumptuous.
Ye are basing your critique on the assumption that you know the reason for the question.

genzo1234 said:

Can someone please tell me the CPU processing speed of ControlLogix L61 and CompactLogix L27ER??

Click to expand...

It's a very straight forward question, which does have an answer.

rdrast said:

...I don't have the time nor the patience to do simple searches for you.

Click to expand...

But yet you found the time to reply, and rudely at that. Why bother? That'll really get newcomers wanting to come back alright!

If the OP has any further questions, hopefully they won't be too afraid to ask again.

"People are strange, when you're a stranger..."

G.

genzo1234 said:

Can someone please tell me the CPU processing speed of ControlLogix L61 and CpmpactLogix L27ER??

Click to expand...

Measured how? I mips, scans time, MHz or GHZ?
CPUs are so powerful now days that speed is rarely an issue for most applications. Now the issue is how to keep the CPU speed up and reduce power consumption. Memory wait states can be a killer and really slow down the CPU. To get that info you would need to see the design and I doubt Rockwell will share that info. You may get a relative speed like 1.2 to 1.

Peter Nachtwey said:

...To get that info you would need to see the design and I doubt Rockwell will share that info.

Click to expand...

Peter,

The specs for these CPUs are in the link I gave above, and no, they are not readily available from Rockwell.

I'll post them here again...

CompactLogix controllers, run on Freescale MCP855T PowerPC microprocessors, namely PowerQUICC.
Their package type is PBGA 357.
They use 32 Bit Power Architecture and feature 50MHz, SoC, CPM, ENET, ATM, HDLC, PCMCIA.
They are the baby of the MCP860 PowerPC family.

Features...

Embedded MPC8xx core with 105 MIPS at 80 MHz (using Dhrystone 2.1)
4-Kbyte Instruction Cache
4-Kbyte Data Cache
8 Kb Dual Port RAM
Instruction and Data MMUs
Up to 32-Bit Data Bus (Dynamic Bus Sizing for 8, 16, and 32 Bits)
32 Address Lines
Complete Static Design (0-80 MHz Operation)
Memory Controller (Eight Banks)
General-Purpose Timers
System Integration Unit (SIU)
Interrupts
Communications Processor Module (RISC CPM)
Four Baud Rate Generators
One SCC (Serial Communication Controller)
Two SMCs (Serial Management Channels)
One SPI (Serial Peripheral Interface)
One I2C (Inter-Integrated Circuit) Port
Time-Slot Assigner
Parallel Interface Port
PCMCIA Interface
Low Power Support
Debug Interface
3.3 V Operation with 3.3V I/O

...

Older ControlLogix up to L6x run on Philips Semiconductor (now NXP) Atlas ARM 32-bit RISC VY22575 microprocessors.

Features...

16-bit/32-bit ARM7TDMI-S microcontroller in a tiny LQFP48 package.
63 MIPS @ 70 MHz (using Dhrystone 2.1) maximum CPU clock available from programmable on-chip PLL with a possible input frequency of 10 MHz to 25 MHz and a settling time of 100 ms.
128-bit wide interface/accelerator enables high-speed 70 MHz operation.
On-chip integrated oscillator operates with an external crystal in the range from 1 MHz to 25 MHz.
2 kB/4 kB/8 kB of on-chip static RAM and 8 kB/16 kB/32 kB of on-chip Bash program memory.
ISP/IAP via on-chip bootloader software.
Single Bash sector or full chip erase in 100 ms and programming of 256 bytes in 1 ms.
EmbeddedICE RT offers real-time debugging with the on-chip RealMonitor software.
The 10-bit A/D converter provides eight analog inputs, with conversion times as low as 2.44 ms per channel and dedicated result registers to minimize interrupt overhead.
Two 32-bit timers/external event counters with combined seven capture and seven compare channels.
Two 16-bit timers/external event counters with combined three capture and seven compare channels.
Low power Real-Time Clock (RTC) with independent power and dedicated 32 kHz clock input.
Multiple serial interfaces including two UARTs (16C550), two Fast I2C-buses
(400 kbit/s), SPI and SSP with buffering and variable data length capabilities.
Vectored interrupt controller with configurable priorities and vector addresses.
Up to thirty-two 5 V tolerant fast general purpose I/O pins.
Up to 13 edge or level sensitive external interrupt pins available.
Power saving modes include Idle mode, Power-down mode with RTC active, and Power-down mode.
Individual enable/disable of peripheral functions as well as peripheral clock scaling for additional power optimization.
Processor wake-up from Power-down mode via external interrupt or RTC.

...

Peter Nachtwey said:

...Memory wait states can be a killer and really slow down the CPU...You may get a relative speed like 1.2 to 1.

Click to expand...

As ARM processors are quite common in the PLC world, this is quite relevant...

Dhrystone and MIPs (Million Instructions Per Sec) performance of ARM processors

The MIPS figures which ARM (and most of the industry) quotes are "Dhrystone VAX MIPs". The idea behind this measure is to compare the performance of a machine against the performance of a reference machine. The industry adopted the VAX 11/780 as the reference 1 MIP machine.

The benchmark is calculated by measuring the number of Dhrystones per second for the system, and then dividing that figure by the number of Dhrystones per second achieved by the reference machine.

So "80 MIPS" means "80 Dhrystone VAX MIPS", which means 80 times faster than a VAX 11/780. The reason for comparing against a reference machine is that it avoids the need to argue about differences in instruction sets.

RISC processors tend to have lots of simple instructions. CISC machines like x86 and VAX tend to have fewer, more complex instructions. If you just counted the number of instructions per second of a machine directly, then machines with simple instructions would get higher instructions-per-second results, even though it would not be telling you whether it gets the job done any faster.

By comparing how fast a machine gets a given piece of work done against how fast other machines get that piece of work done, the question of the different instruction sets is avoided.

There are two different versions of the Dhrystone benchmark commonly quoted:

Dhrystone 1.1
Dhrystone 2.1

ARM quotes Dhrystone 2.1 figures. The VAX 11/780 achieves 1757 Dhrystones per second.

- The maximum performance of the ARM7 family is 0.9 Dhrystone VAX MIPS per MHz.

- The maximum performance of the ARM9 family is 1.1 Dhrystone VAX MIPS per MHz.

These figures assume ARM code running from 32-bit wide, zero wait-state memory. If there are wait-states, or (for cores with caches) the caches are disabled, then the performance figures will be lower.

To estimate how many ARM instructions are executed per second then simply divide the frequency by the average CPI (Cycles Per Instruction) for the core.

- The average CPI for the ARM7 family is about 1.9 cycles per instruction.

- The average CPI for the ARM9 family is about 1.5 cycles per instruction.

Regards,
George

My first impulse as an answer to the original question was "12". Just to see what the response would have been. Then perhaps we could have gotten some context. Oh well....next time. Y'all are just too information and helpful.

OG

Well I would have seen the funny side to that reply OG!

Whatever. Even the answer you posted Geospark is essentially useless. Once more, stating the raw processor power is pointless. A powerful processor can be crippled by an inefficient operating system, or even more so by an inefficient user program. Likewise, a limited processor can run like wild fire with an excellent OS and program.

In any event, the 'Speed' of a PLC CPU ultimately has very little to do with the clock speed of the CPU.

A PLC in a particular class, the PAC types (since he is looking at the Logix Platform) is going to be functionally equivalent whether you use AB, or Siemens, or Automation Direct, or any other supplier of PAC Class architecture.

If you need absolute raw microsecond scan speeds, then you start looking at a dedicated, custom system, or a motion controller like from Delta.

Everything is application determined.

/shrug.

Let's not fall out here.

rdrast said:

...the answer you posted Geospark is essentially useless...

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As was their question?

You're entitled to your opinion, but in the same vein as my story, you're saying it's a pointless question to have asked, so why bother even answer it. It could be pointless, useless or meaningless info to you, but relevant, useful or even fascinating info to another reader. It all depends on what a reader wants it for, or takes from it.

rdrast said:

...the 'Speed' of a PLC CPU ultimately has very little to do with the clock speed of the CPU.

Click to expand...

I think you meant this the other way around?

But your right, the clock speed of the CPU, alone, does not determine the actual speed of processing the data. There are many other factors to consider when comparing the performance of CPUs, like the width of the data bus, the latency of the memory (as Peter pointed out), and the type of cache used. These two particular processors implement different architectures, so even if they had the same clock rates, etc., they are quite incomparable at the hardware level. Clock rates can sometimes be misleading since the amount of work different CPUs can do in one cycle varies. That's why the clock rate, etc., alone, generally are considered to be an inaccurate measure of performance when comparing different CPU families. Software benchmarks tend to be more useful.

So you see, I agree with you for the most part. That's why I said "I do understand yere point of view". It's quite possible they are trying to compare CPU speeds to decide which is best for an application. But the point I am making still stands. If we don't know why the OP requires this info, we cannot presume to know that this info, on it's own, is useless to them, or anyone else reading it for that matter.

Give them the info they requested, if you have it. Then if you want, advise them that if they are looking to base application speed on CPU speed, then there are other factors to consider, but you shouldn't dismiss them in such an off-handed manner.

Your last reply would have been a far better and more useful reply than your first.

Peace,
George

The processing speed depends on the PLC program size, I/Os and other ethernet devices in the system reading tags. The program is done "continuous" by default but you can change it periodic or event based. It might help speed up processing time but you need to make sure the RPIs do not overlap. There is also a check box "Disable Automatic Output processing... " which can be tried to speed up processing.

Jothiswarup said:

The processing speed depends on the PLC program size, I/Os and other ethernet devices in the system reading tags. The program is done "continuous" by default but you can change it periodic or event based. It might help speed up processing time but you need to make sure the RPIs do not overlap. There is also a check box "Disable Automatic Output processing... " which can be tried to speed up processing.

Click to expand...

Kind of doesn't apply to PACs, which is what rdrast was alluding to in his reply. PACs, like the Control and Compact Logix family, have separate processors for program execution and I/O image processing. The issues you mention would be relevant to a PLC, which is using the same processor for both functions. The Compact and Control Logix products are not "PLCs" any longer.

Which gets back to begging the question of the OP "Why do you ask?". The validity of asking "Why" here has to do with attempting to provide MEANINGFUL information. If genzo1234 (who now appears to have been scared off) was attempting to make comparisons of the A-B PACs to a PLC from someone else based on "processor speed", it is an erroneous comparison from the outset. Whatever number you assign, be it clock speed GHz, MIPS, MFLOPS, Scan Time, Moose Turds per Mouse Flatus etc. etc., will be irrelevant in that if there is a difference in execution rate of the tasks YOU want to accomplish, it most likely will not directly translate to the assigned acronym anyway.

jraef said:

...If genzo1234...was attempting to make comparisons of the A-B PACs to a PLC from someone else based on "processor speed", it is an erroneous comparison from the outset...

Click to expand...

Of course it is, but you still don't know why they asked as you say, so you cannot assume it was asked for that reason. I answered the question at face value. But my link also provides instruction execution times for various controllers to provide more meaningful info along with the raw CPU specs.

If they asked for more info with regard to application speed, then I, or I'm sure others would have obliged.

I think ye are mis-reading my intentions here?
I'm not saying we shouldn't ask why, just that we shouldn't assume the obvious until we get that reason.

I fully understand the varying affects that the end-user's application will have on the performance of any PLC/PAC. The simple point I am making is that from the outset an assumption is being made that they must surely be seeking this info for a comparison either between the two AB PACs, or between these AB and some other brand PLCs or PACs. This may or may not be the case, that is all I'm saying. The OP has only this one post here, so we have no previous insight into their background or field to help provide some context. They could be doing a thesis, a historical study on what CPU speeds were chronologically used by AB, or others. They could be writing a book. They could be doing a bench-test and need the manufacturer's rated speed as a base, who knows why?...

They know why, and if they never come back now, we may never know.

G.

Geospark that is very interesting information about the Logix CPUs. Do you know about the L7x cpu?