Just starting with PLC 5

I have worked some with SLC 500 and ControlLogix and now am starting to work with a PLC 5. Does anyone have some good advice or know where a good resource is on addressing in RSLogix 5?

Also what are the basic differences from SLC 500 or ControlLogix?

Addressing between SLC and PLC5 are virtually the same, some nuances but the programming environment between RSLogix500 and RSlogix5 is virtually identical. If you know one environment you'll pickup the other without a problem.

If you have already worked with a SLC and ControlLogix, your question of "what are the basic differences" escapes me. One would think they would be quite noticeable.

In my opinion, the biggest difference is in the I/O addressing.

The PLC-5 adopted the old Allen-Bradley Universal Remote I/O protocol that had been in use since the late 1970's in the PLC-2 and PLC-3 platforms. Because it was built around 8-channel I/O cards, RIO data tables use Octal (Base 8) addressing.

The bits on an I/O module are numbered 0, 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17.

This can get a little confusing because the rest of the 16-bit integer datatypes used by the PLC-5 are in Decimal (Base 10). The ninth bit of an Input module is "I:030/10", but the ninth bit of an Integer word is "N7:0/8".

Get the PLC-5 Instruction Set Reference and the User Manual for the variety of PLC-5 you are using (probably the "Enhanced and Ethernet Controllers User Guide"). Both are handy to have in hardcopy.

Other differences include the way Main Control Programs run (SLC has only Program File 2, but PLC-5 has MCP A through P) and the way interrupts work. The PLC-5 has very large communication buffers and I/O capacity, but lacks channel-to-channel passthrough. PID equations function slightly differently. The SLC is generally faster solving logic. PLC-5 has sequential function charts but they are seldom used.

But as you have seen, much of the instruction set and the RSLogix development environment are very similar, making it easy for Allen-Bradley programmers to move from one platform to another.

Paully's5.0 said:

Addressing between SLC and PLC5 are virtually the same,

Click to expand...

Not quite, PLC5 uses octal addressing for I/O files. Bits 9 and 10 are not there.

See PDF below, ( ignore the $ sign (Logical Address Identifier) in front of the addresses)

And another "slight" difference between the PLC and SLC platforms:

PLC5 I/O module's types are not part of the RSLogix 5 application file (like the 1747 SLC type ones), nor the controller ensures the modules' connectivity at Runtime! Replacing an SLC I/O module with a different one than the type stated within the RSLogix 500 application file's I/O Configuration will invariably fault the CPU, hence the user needs to be accurate but not too vigilent.
The user of a PLC5 system should be extremely careful when replacing any 1771 I/O module since, if the replacement module carries a different type, the system will keep running with potentially catastrophical results.

For the PLC/5 you need to make sure you are absolutely clear on the different meaning of Chassis and Slot verses Rack and Group. The terms are nearly synonymous in the SLC500 system. They mean something different on a PLC/5. You also need to get it clear in your head that unlike the SLC-500 system IO is not addressed by the chassis and slot. In the PLC/5 system IO is addressed by Rack and Group. I bring this up because its something that SLC-500 programmers stumble over again and again.

Review the PLC/5 addressing manual. Also here are some threads on the topics.

http://www.plctalk.net/qanda/showthread.php?t=21174

http://www.plctalk.net/qanda/showthread.php?p=124847#post124847

Hi

If you look at an I/o address it breaks down to rack,rack,group
So I:011/0 is actually rack 0 rack1 group1 and then bit 0.
Another is if you have an E on the end of he processor type like 5/40 E
This has Ethernet built in but you use the 25 pin port with a (sorry someone will use the correct name) converter and you can not connect with the 25 pin cable you would use in 5/40 controller as this will be a serial port.
The other differance is the price of the plc 5 parts vers the slc it's way more.
In the part of the world plc 5 is really dying fast as the slc not as quick as I believe due to the micro logix range using the same software
I remember using trends in the logix 5 can't remember that in slc but I am not sure.

Donnchadh

Mickey said:

Not quite, PLC5 uses octal addressing for I/O files. Bits 9 and 10 are not there.

Click to expand...

That's why I didn't use term "identical"

Hi,

Using PLC-5, is there a way to use GSV to retrieve memory usage from the controller?

INI

Hi

Not sure you can get the memory usage but if you can you would not use a gsv.
If you look at the project tree you will see A s: file. This is where all the processor status bits, time and date etc are. Now do you just want to see the memory usage or do you want to display it. If you just want to see it I think it's under controller properties in the project tree

Donnchadh

PLC5 does not have a "GSV" instruction.

The memory usage can be viewed under controller properties within RSLogix5 software. See picture.

I am not aware of a status register for those values.

EDIT: Donnchadh types faster then I do.

Thanks everyone for your time and effort. Your input is very helpful as I am a student and trying to get as much learning as I can in the time I am here (at school).