User guide

Software
890 USE 108 00 August 2001 53
The Compact Instruction Set
Overview The Compact instruction set is dependent on the Compact model:
The A984-1xx, E984-24x/251/255 supports 984 ladder logic only. In contrast, the
E984-258/265/275/285 supports 984 ladder logic and IEC 1131-3.
The specific instructions listed below are available for the A984-1xx, E984-24x/
251/255, and E984-258/265/275/285 models as noted.
984 Ladder Logic
(A984-1xx, E984-
24x/251/255
Only)
Resident in the executive firmware of the Compact Controller is a set of six ladder
logic programming elements and several ladder logic programming instructions that
depend on the controller model.
MSTR and CKSM are never available together. All compacts (A984-145, E984-245/
255) that use Modbus Plus use MSTR. All others use CKSM. Compact models
E984-251/255 use XMRD and XMWT. Therefore, all compacts except E984-245/
255 have 36 functions and the E984-245/255 Compacts have 38 functions.
984 Ladder Logic
& IEC 1131-3
(E984-258/265/
275/285 Only)
Resident in executive firmware of the E984-258/265/275/285 Controller is a set of
six ladder logic programming elements and more than 80 ladder logic programming
instructions.
The following table lists the standard ladder logic programming elements.
For more information about these instructions, see the Modicon Ladder Logic Block
Library User Guide (840 USE 101 00).
Symbol Meaning
-| |- A normally open contact
-|\|- A normally closed contact
-|=|- A positive transitional contact
-|O|- A negative transitional contact
-( )- A normal coil
-(L)- A latched or memory-retentive coil