ABB / AC500 / PM processor modules

Memory is the obvious difference between AC500 CPUs. Instruction speed is the one that actually decides whether a replacement works, and there is a twelvefold step in the middle of the range.

The PM processor module is the expensive part of an AC500 station and the part people get wrong when substituting. This page gives the order codes, the memory, the instruction times and the interface count so you can compare properly.

The speed step nobody expects

Look at the binary instruction times before the memory figures.

The jump between PM582 and PM583 is the significant one in the whole range. It is not a small increment, and it is not visible in the model number.

The floating point difference is larger still. A PM573 takes 0.5 microseconds per floating point instruction; a PM583 takes 0.008. That is over sixty times.

So if an application does real arithmetic, PID loops, scaling or recipe maths, the CPU tier matters far more than the memory figure. Moving up from a PM573 to a PM583 is a performance change, not just a capacity change.

Full PM comparison

From the ABB AC500 catalogue. Instruction times are binary, word and floating point.

Weight is around 0.150 kg across the range, and 0.135 kg on the PM582.

PM582 and PM583 have the same memory

Both are 1024 kB. The entire difference between them is speed. If someone specified a PM583 rather than a PM582, it was for performance, and swapping down loses it while the program still fits.

That is the substitution most likely to appear to work and then cause scan time problems under load.

The PM591-ETH trades a serial port for an Ethernet port

Worth catching before ordering. The PM591-ETH has two Ethernet interfaces and only one serial port, where every other CPU in the range has two serial.

If the existing station uses two serial connections, a PM591-ETH will not accommodate them. The PM591-2ETH has one Ethernet and two serial instead.

Two similar model names, opposite interface arrangements.

A note on published memory figures

You will find different memory figures for the same CPU depending on the source. Reseller listings and ABB catalogue tables do not always agree, and the ABB data sheet gives a more detailed breakdown again.

For example, the ABB data sheet describes the PM591 as 3584 kB including 1536 kB buffered, where the catalogue table lists 4096 kB. Those are different measures of the same device: total integrated memory against user program and buffered data.

We work from the ABB data. If the exact usable memory matters for your application, tell us and we will confirm it against the current ABB data sheet rather than a catalogue summary.

The same caution applies as on the ACS550 page, where current codes differ between catalogue revisions.

The suffix decides the interfaces

A PM573 and a PM573-ETH are different parts. Order the plain version to replace an Ethernet one and the network connection is gone.

And remember from the AC500 page: the XC version carries no marking. A part number beginning 1SAP3 is the extreme conditions version.

PM595, the top of the range

ABB specifies the PM595 with two Ethernet interfaces with an integrated switch and software configurable protocol, supporting PROFINET and EtherCAT, plus two independent Ethernet interfaces.

So four Ethernet ports in total, two switched and two independent. Available as PM595-4ETH, optionally followed by -F or -M.

The software configurable protocol matters. The same hardware can be a PROFINET or an EtherCAT device depending on configuration, which is unusual and worth knowing when specifying.

AC500-eCo processor modules

PM554 and PM564 have no built-in real time clock. ABB supplies the TA562-RTC as a separate option for exactly those two CPUs.

If the application timestamps data or runs a time schedule, check whether that module is fitted, because a replacement CPU will not include it.

The eCo range is a different physical format from the modular AC500. An eCo CPU does not fit a TB5xx terminal base. Moving between eCo and modular AC500 is a station rebuild, not a CPU swap.

Current generation PM CPUs

These use the TB5600, TB5610 and TB5620 terminal bases rather than the TB51x to TB54x range.

That is a terminal base change, not just a CPU change. Moving from a PM59x to a PM56xx means replacing the base, which means rewiring.

Earlier and specialty CPUs

Shared specifications

Three years of battery retention is the number to diarise. If nobody knows when the TA521 battery was last changed, change it while the plant is running rather than discovering it during a power outage.

The clock drift of two seconds a day is worth knowing too. That is around twelve minutes a year, so any application relying on timestamps needs a time sync rather than the internal clock alone.

Communication module capacity

Useful when planning a station. ABB states there are no restrictions on communication module types or combinations, giving the example of up to four PROFIBUS DP communication modules in one station.

So the limit is the terminal base slot count, not a rule about mixing protocols. A TB541 with four slots can carry four communication modules in any combination.

See the AC500 page for the terminal base slot table.

Choosing a replacement CPU

Match the suffix first. ETH, 2ETH, ARCNET or none. This decides what you can connect to.

Then check speed, not just memory. A PM582 and a PM583 both have 1024 kB and differ by a factor of twelve on instruction time.

Count the serial ports. The PM591-ETH has one where most have two.

Check the order number for 1SAP3. That means XC and the module looks identical to a standard one.

Check the terminal base. A PM56xx needs a TB56xx. A PM59x needs a TB51x to TB54x.

Ask whether the program still fits and still runs in time. Moving down a tier can leave a program that loads and then overruns its scan.

The configuration is not in the CPU you buy

A replacement PM module arrives blank. Without the original project file the station will not run, and an AC500 project is not something to recreate from scratch under outage pressure.

If you run AC500 anywhere, the question worth asking today is whether the project files are backed up and whether anyone knows where they are. Same point as the PNOZmulti configuration and the mGuard settings on our Factoryline page.

What we can supply

Current production. The full PM range including PM56xx and PM5xxx generations, eCo CPUs, terminal bases and accessories, in standard and XC versions. Quoted with a delivered lead time.

Discontinued and superseded. PM571, PM572, PM581, PM582 and earlier modules, plus EC581 and EC583. Surplus and tested used.

Accessories that go missing. TA521 batteries, MC502 memory cards, TA562-RTC clock modules and TK50x programming cables.

We buy AC500 CPUs

PM modules hold value, and the older ones are worth more to a plant still running them than they are as scrap. See Sell To Us.

Related

ABB overview. AC500 controllers and S500 I/O for terminal bases, I/O and communication modules.

For controllers from other brands see Siemens S7-1500, CompactLogix and Omron Sysmac.

Send us your order codes

Send the 1SAP number where you have it. Tell us what the CPU is connected to, because the interface count differs across models that otherwise look alike. Quotes in NZD including GST.

Request a quote

Industech is an independent supplier of new, surplus and used industrial automation equipment. We are not an authorised distributor of, approved by, sanctioned by, or affiliated with ABB Ltd. ABB and AC500 are trademarks of ABB Ltd. All trademarks, brand names and order codes are the property of their respective owners and are used here for identification purposes only.