John,
Have you used the PLC Integration blocks? I'm no expert by any stretch of
the imagination, but they do seem to have features that help. For instance,
1. The PLC integration blocks can use the native AB address to
reference the data they read/write, e.g. B01:12:15 This makes it easier to
track the connections
2. The PLC integration blocks are specifically designed to pass
operator commands through the I/A station to the PLC and to see status
coming back. They will "write once" the command upon receipt from the WP,
rather than writing to the PLC every cycle. This should eliminate a number
of problems with multiple interfaces changing the same value, e.g., the use
of PanelView and I/A Series WPs to change the same register.
3. There are some combined PLC integration data structures that allow a
mix and match of different input and output point types, so that the same
block name can serve as the tie point for an operator graphic. This also
helps eliminate multiple blocks for a single function.
4. The PLC integration blocks are far simpler, few parameters, almost
no algorithm - so they can enable things like running faster BPCs.
Do you find them to be useful. They are in V6.2.1 for AW50-I, AW70-I, and
Micro I/A.
Regards,
Alex Johnson
The Foxboro Company
10707 Haddington
Houston, TX 77043
713.722.2859 (v)
713.722.2700 (sb)
713.932.0222 (f)
[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>
-----Original Message-----
From: John Metsker [SMTP:[EMAIL PROTECTED]]
Sent: Tuesday, May 09, 2000 1:34 PM
To: '[EMAIL PROTECTED]';
'[EMAIL PROTECTED]'
Subject: RE: RE: Integrator 30's vs. AB Stations
Neil,
Some thoughts on your questions
>From reading the AB emails, it sounds like some of our future
directions should
>be:
>1. Work towards installing AB PLCs with an Ethernet interface.
>2. Use the Foxboro Micro I/A or an AW to provide desired
interfaces to Foxboro
systems. We do not need PLC redundancy.
1. The world is definitely gone Ethernet. It is hard to
believe that any control/automation equipment that be installed in 2000
would not provide an Ethernet port as a physical connection.
2. The AW-I's (51 or 70) now and Micro I/A as part of a late
release to 6.2.1 are Foxboro products that provide Ethernet connectivity to
AB PLCs. I am not a fan of Micro I/A solution. It is a Foxboro proprietary
interface to AB. The AW-I's are products that use 100% unadulterated
Interchange or RSLinx from Rockwell. Yes, Foxboro has still developed the
ECB application to talk to the PLCs, but the framework of that application
and the underlying communications is provided by the AB software that is
used. You sound like you have quite a mix of AB products to deal with. You
will probably have to entertain using Ethernet integration devices such as a
Pyramid Integrator (PI) (old) or a Control Logix gateway (new) to
communicate to your DH+ based PLC's and the DH485 based SLC's. I don't
believe (I haven't seen it advertised) that the Micro I/A solution supports
communication through a PI since Foxboro ported just the low level portions
of Interchange to VRTX. I know it won't support communication to Control
Logix since a different protocol stack is required. (EPIC) These are
features that the AW-I's do provide. I can't stress it more, however, it a
station is performing 'control' (and I consider the communication back and
forth to PLCs to be control), keep this functionality isolated.
>1. What is the best way to provide process operators and engineers
a view of
what is happening in the PLC in an easy to understand manner with
minimal
upkeep.
Allow the PLC to do what is best at, discrete control, and
allow the DCS to do what it is best at, analog control. Make sure this
division/sharing of control is understood by your process operators and
maintenance technicians.
>2. We would like to implement some software that makes Allen
Bradley PLC
programming as easy as possible and also that provides logic
documentation that
is very easy for non relay logic experts to follow. Any
suggestions?
Keep a consistent bit packing scheme for all your discrete
devices, e.g. motors, valves between I/A and the PLC. We use a MCIN (2
words, 32 bits) for each device as inputs from the PLC and an MCOUT (1 word,
16 bits) as outputs to the PLC.
MCIN
MCOUT
1st bit A/M status A/M command
2nd bit Status 1 (Hold contact 1) Start/Open command
3rd bit Status 2 (Hold 2 on 2 pos. device) Stop/Close command
4th bit General Fault Fwd/Rev command
... ... ....
The inputs from the PLC are packed in one file (e.g. N110) and the
outputs to the PLC in another (e.g. N120) Assign the starting word of for
each device to be the same in both the input and output files. Inputs from
valve XV22007 begins at word 20 in N110 and outputs to the valve begin at
word 20. Yes, 1 output word would go unused, but the consistent device
addressing is more important. Use standard overlays for the devices
illustrating your standard data pack scheme so the majority of the PLC
troubleshooting can be done right from the I/A screen. Make sure the
address scheme documents itself within the overlay.
>3. The purpose of most of our PLCs is for external shutdowns
(SIS). Will
Control Logix provide any real benefit? Is Control Logix considered
to be
robust enough for SIS, or should it be used in conjunction with the
PLCs?
The Control Logix platform is Rockwell's new PLC product that
integrates sequential/discrete, motion, and process control (with the
Process Logix module) on the same backplane. They certainly wouldn't claim
that is any less robust than a PLC5. A couple years ago when it was first
introduced, however, AB was pretty good at saying that it wasn't ready to
move the PLC5 aside just yet. Like anything else, it is the programming
tools such as RSLogix 5000 that are taking a little longer to mature.
>4. If we network our PLCs together in some manner, will it keep us
from also
using Micro I/A or an AW to somehow interface designated PLCs to
designated
Foxboro systems?
Create dedicated "control LAN segments" to handle the communications
between Foxboro and your PLCs. A huge amount of bandwidth is not required,
but remember you are expected to provide near real-time response so keeping
these segments as lightly loaded as possible and isolated from other network
garbage (X protocol, print jobs, ftp's, etc..) is important. Join these
segments to your corporate network to do network device management (hubs,
switches) and create a data path if you are performing remote programming or
PLC backups (MDT Mass).
>5. Besides the purchase of the AW, what all do we need to purchase
to use an AW
for the interface? Does it matter whether we use a Unix or NT AW?
The AW-I's would require Interchange for Unix or RSLinx for NT. At
this point, there is no functional difference between the AW51I and the
AW70I in regard to the AB capabilities. Stay with what you are comfortable
with. Either is fine for now. We are staying with the 51's since that is
consistent with our install base. Since Rockwell is so NT dominant, the
AW70 may give you more future growth potential in regard to Control Logix,
but it would be up to Foxboro exploit this capability through new ECB's and
block types.
Hope this begins to address your questions.
John
-----Original Message-----
From: [EMAIL PROTECTED] [ mailto:[EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]> ]
Sent: Monday, May 08, 2000 2:35 PM
To: John Metsker; 'Foxboro DCS Mail List'
Subject: Re:RE: Integrator 30's vs. AB Stations
John,
Thank you for taking the time to provide the information concerning
Allen
Bradley PLCs. I thought it was very informative.
As of last week, my group will start to take on our facility's AB
PLC
responsibilities in addition to our current Foxboro I/A support. I
know little
about the Allen Bradley product so I have a steep learning curve
ahead of me.
My goals are to some how network the PLCs together for information
transfer and
remote support purposes, and to implement some software that makes
the PLC
programming much easier (than the relay logic look) to implement and
documents
the logic for non-experts to easily follow. I would appreciate any
tips that
you and others can provide to me.
I do not even know what Allen Bradley product we have yet, but I
think some of
them are SLC150, SLC5/04, PLC5/11, PLC5/20, and a Panel View (??)
station. The
PLCs are scattered around the facility on process equipment that is
controlled
various independent Foxboro systems and few, if any of them, are
currently
networked together. We will want some of the Foxboro systems to
somehow get
information from PLCs that are installed in their area, but we also
want to be
able to access all of the PLCs from common designated locations (say
designated
Office PCs with the correct security). One of the reasons to link
the PLCs to
the Foxboro systems will be to provide PLC trip alarms,
historization of the
contact states in PI, and a better means for the process operators
and engineers
to somehow view the states of the PLC logic.
From reading the AB emails, it sounds like some of our future
directions should
be:
1. Work towards installing AB PLCs with an ethernet interface.
2. Use the Foxboro Micro I/A or an AW to provide desired interfaces
to Foxboro
systems. We do not need PLC redundancy.
Some of my questions are:
1. What is the best way to provide process operators and engineers
a view of
what is happening in the PLC in an easy to understand manner with
minimal
upkeep.
2. We would like to implement some software that makes Allen
Bradley PLC
programming as easy as possible and also that provides logic
documentation that
is very easy for non relay logic experts to follow. Any
suggestions?
3. The purpose of most of our PLCs is for external shutdowns (SIS).
Will
Control Logix provide any real benefit? Is Control Logix considered
to be
robust enough for SIS, or should it be used in conjunction with the
PLCs?
4. If we network our PLCs together in some manner, will it keep us
from also
using Micro I/A or an AW to somehow interface designated PLCs to
designated
Foxboro systems?
5. Besides the purchase of the AW, what all do we need to purchase
to use an AW
for the interface? Does it matter whether we use a Unix or NT AW?
Regards,
Neil Martin
Huntsman Petrochemical
____________________Reply Separator____________________
Subject: RE: Integrator 30's vs. AB Stations
Author: John Metsker <[EMAIL PROTECTED]>
Date: 05/08/2000 1:05 PM
Sorry for being late to the mix and continuing to drag out this
issue. This
discussion should be linked to the e-mail flurry about AB Control
Logix and
Ethernet connectivity from a month or so ago. (I would assume that
your AB
connectivity strategies need to include support for the new AB
product
directions.)
At General Mills, we are using AW51 Integrators to provide AB
gateway
functionality. Yes, the Foxboro software bundling says that it is
an AW and
it can act as an all in one machine, but they are being deployed as
"dedicated" Integrators. (Basic premise of distributed control;
keep
"control" separate from everything else. We may be a food company,
but
we're not stupid.)
How come? Seems like overkill doesn't it.
AB Interchange from Rockwell Software and Ethernet connectivity.
(The AW 70
Integrator cousin uses RSLinx.)
Why would anybody want AB connectivity that doesn't utilize the
standard
communication libraries that are developed and tested by Rockwell
software?
Every other major software vendor (Wonderware, Intelluion, MDT, SAP,
etc..)
that communicates with AB equipment develops applications that
utilize
RSLinx or Interchange. Why should Foxboro be different? Foxboro is
no
great lover of PLCs and Allen Bradley/Rockwell in particular. Their
products should have a headstart and take advantage of the
connectivity that
is provided by Rockwell themselves.
Why not any of the other AB connectivity products from Foxboro?
ABGW or the ABGW30? The serial interfaces are too much of a bottle
neck.
The food industry is largely a discrete industry, we need to
communicate a
lot of data at Ethernet bandwidth to/from the PLCs. The ABGW and
ABGW30
hardly allows a lot of PLC words to be communicated at high speed.
(Don't
have redundant PLCs, don't need a redundant PLC interface.)
AB Station? The 1 to 1 coupling of AB stations to PLCs tends to
promote use
of "data concentrators" that add complexity to PLC troubleshooting.
The
sideport on the PLC provides about 1/2 the throughput that the
integrated
Ethernet port on PLC5E. (Ask to your knowledgeable AB rep to
compare
Ethernet performance on an integrated PLC5E to an Ethernet sidecar.)
The AB
coprocessor is has a Motorola 68030 chip in it. That is it for that
product
from AB. They assume everybody utilizing host computers with RSLinx
or
Interchange to accomplish the jobs once handled by the co-pro
module.
How 'bout Micro I/A with AB Ethernet? The product is now going to
be a
'late release' item with V6.2.1. Foxboro developed this product by
licensing source code from Rockwell and porting the low-level parts
of it to
the VRTX O.S. that runs in Micro I/A. It is now a Foxboro
proprietary
product. Also, be aware that Control Logix uses a different network
protocol stack than PLC5s. Foxboro's VRTX port of Interchange was
prior to
a version that supported Control Logix. Foxboro is going to have to
completely start over with this product in order to work with CL.
(The
forthcoming Micro I/A AB Ethernet interface for PLC5/SLC500 has now
been in
the works for over 3 years.)
AW51 Integrator? It is able to support Control Logix with the
installation/configuration of the proper, underlying version of
Interchange
(V6.2) It provides a 1 to many Ethernet interface to PLCs. Sure it
has
draw backs, like a hard drive and not being redundant. The Ethernet
connectivity hopefully allows the box to sit in as decent an
environment as
possible and as the prevailing chat on the email list would
indicate, it is
not the stability of the hardware, but the stability of the software
that is
afflicting the Foxboro User community. Redundant hardware can't
help there,
but deploying the machine as simply an "Integrator 51" and reducing
the
functionality of it improves it's stability greatly.
Oh yea, the price. Well, let me be the first one to tell you that
the price
of cereal will be going up. Foxboro marketing needs to be involved.
A full
AW station license should not be charged if a 51 series machine if
is going
to be utilized as an "Integrator 51". A Gateway software bundle for
the 51
was in the works as part of V6.2, but that was dropped like so many
other
things have been. The hardware part of it will forever perplex me.
Why can
Foxboro develop/manufacture there own proprietary DIN rail computer
and sell
it at a somewhat desirable price, but they have to sell a Sun box at
double
or more of the street price.
Anyway sorry for being long winded. I hope this provides some
different
perspective on Foxboro/AB integration strategies. Your feedback is
appreciated.
Thanks,
John Metsker
General Mills, Inc
-----Original Message-----
From: Johnson,Alex [ mailto:[EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]> ]
Sent: Thursday, May 04, 2000 10:17 AM
To: Foxboro DCS Mail List
Subject: RE: Integrator 30's vs. AB Stations
Re: PSS
Check with your account rep or, you can get if from
www.csc.foxboro.com
< http://www.csc.foxboro.com <http://www.csc.foxboro.com> > . I just
checked and if you search for "PSS
21H-6C6 B4" on the CSC page it will take you to a list and this
document was
the second one on the list.
Re: Redundancy
The Micro I/A solution is not redundant that I am aware of, but you
can
always go point to point just like with the DI30 and have only one
PLC per
Micro I/A.
Regards,
Alex Johnson
The Foxboro Company
10707 Haddington
Houston, TX 77043
713.722.2859 (v)
713.722.2700 (sb)
713.932.0222 (f)
[EMAIL PROTECTED] < mailto:[EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]> >
-----Original Message-----
From: Stan Brown [SMTP:[EMAIL PROTECTED]]
Sent: Thursday, May 04, 2000 8:40 AM
To: [EMAIL PROTECTED]
Subject: Re: Integrator 30's vs. AB Stations
On Wed May 3 17:20:05 2000 Johnson,Alex wrote...
>
>To learn about Micro I/A check out the following PSSs or
contact
your
>Account Rep. I really think that Micro I/A is a good way to
go for
>integrating the devices that it supports.
>
>PSS 21H-6C6 B4: Micro-I/A Allen-Bradley PLC5/E
Remote I/O
Interface
>
Alex, I am having a hard time finding this PSS. Have
you got
a link, or
something for it?
And a question, if we were to go with the Micro-IA
PLC ->
Ethernet
solution what redunandcny could we incorporate?
--
Stan Brown [EMAIL PROTECTED]
843-745-3154
Charleston SC.
--
Windows 98: n.
useless extension to a minor patch release for
32-bit
extensions and
a graphical shell for a 16-bit patch to an 8-bit
operating
system
originally coded for a 4-bit microprocessor, written
by a
2-bit
company that can't stand for 1 bit of competition.
-
(c) 2000 Stan Brown. Redistribution via the Microsoft
Network is
prohibited.
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