PDA

View Full Version : AB Scan time


Alan Case
June 5th, 2002, 08:27 AM
I just checked the scan time on an AB ML1200 with a medium size program. The number was 11 and it was for a scale of 100 usecs.
ie 1.1 millisecs
Does this seem right as it is a lot faster than an SLC.

Regards Alan Case

Mike
June 5th, 2002, 03:09 PM
Alan,

This is sound correct. The SLC is a dog when it comes to speed, but if you really want to see a fast PLC look at the Omron CS1 or CJ1 they have a speed of .04 nano sec. per basic instruction! If you need speed they have it with some to spare.

Ken Roach
June 5th, 2002, 06:25 PM
Actually the MicroLogix 1200 is slower than the SLC-5/03; about 2 milliseconds /K of program instead of 0.9 ms/K on the SLC.

You're just not running a very big program in the little controller, I suppose. There are two status registers, one for "max scan time" and one for "last scan time". As you add operator interface and floating point instructions you'll see the Max Scan time rising.

The MicroLogix 1200 and 1500 are better at this kind of reporting than their predecessors; the MicroLogix 1000 couldn't report it's scan time if it was under 10 milliseconds (which most were !).

The CJ1 is an absolute screamer, but watch your math; it's 40 nanoseconds = 0.040 microseconds per boolean instruction.

Alan Case
June 6th, 2002, 10:18 PM
The program size is approx 1700 words with a max scan time of 2.2 milliseconds and a last scan time of 1.1 milliseconds. An SLC 503 program of mine has only 700 words and a scan times of 23 and 13 milliseconds respectively. Neither of the processors have any interfaces connected (ie HIMs) although the micrologix is communicating on a DH485 network. Regards Alan

Operaghost
June 7th, 2002, 01:42 AM
That sounds really excessive for the 5/03 Alan. Unless you are doing tons of data moves those times sound way too long. Care to supply any details on that prog? I'd love to try it on my test bench to see what it does on a 5/03 or 5/04 or 5/05.

OG

Peter Nachtwey
June 9th, 2002, 12:52 PM
Originally posted by Mike
The SLC is a dog when it comes to speed, but if you really want to see a fast PLC look at the Omron CS1 or CJ1 they have a speed of .04 nano sec. per basic instruction!


.04 nano seconds is 25 GHz. I DON"T BELIEVE IT! Intel can't do that yet by a a factor of ten.
.04 micro seconds is 25 MHz which is typical microcontroller speed.