COMMUNICATION between EPICS and the Allen Bradley SLC 500

['Ernest L. Williams Jr.' <williams@mhattcat.howard.edu>]

* The Equipment Protection System (EPS) Status will be sent to EPICS via a 
6008-SV1R VME Allen Bradley Remote I/O Scanner.  The scanner (i.e. a 
6008-SV1R) actually talks to the SLC 500 remote I/O via a Direct 
Communications Module (i.e. a 1747-DCM).  The DCM module has an input image 
table and an output image table.  Each table contains eight 16-bit words. 
The first word in each table is reserved for the status word.  The 
remaining seven words are used for data.  Implementing ladder logic for the 
DCM is very simple and is described in the user manuals.  However, VME 
scanner is implemented with EPICS and is not so straight forward on how 
data is actually getting captured.  Apparently we are only able to choose 
AB-Binary input device type in EPICS.  This device type apparently reads 
8-bit chunks of data.  This means that the first 8-bit chunk is denoted by 
card 0, the second 8-bit chunk is denoted by card 1, and so on and so 
forth.   So far, things are working great as long as I choose AB-Binary 
input device type.  Therefore the questions is how are the other Allen 
Bradley (bi) device types used ?

      ANSWER:  Since most SLC 500 Chassis can be set up as '1- slot 
addressing'  one can use the scheme on page 5 of the EPICS: Allen Bradley 
Driver and Device Support documentation.  This  documentation can be found 
at URL address: 
(http://www.aps.anl.gov/asd/controls/epics/EpicsDocumentation/WWWPages/H  
ardwareNoFrame.html#Allen_Bradley)

When using the 1747-DCM the formula used for card selection in gdct is as 
follows:

Card = word*2,  where word corresponds to one of the eight words in the 
DCM's output image table.
Signal = bit location within the word.
Since each word in the 1747-DCM is 16 bits, it makes since to use the AB-16 
bit BI device type in EPICS.

This works great now.

Marty Kraimer, Mark Rivers, Josh Stein, and Chris Seavers were all 
instrumental in helping me resolve this issue of how to make EPICS talk to 
my SLC 500 Chassis.

Thanks,
Advanced Photon Source
MHATT-CAT
(630)252-0209

Ernest

P.S.  Marty can you forward this on to 'tech talk'