Allen-Bradley PLC-5 User Manual page 256

16-4 Using Main Control Programs
In this Field
Program file
Disable
Skip I/O update
Publication 1785-UM012D-EN-P - July 2005
Do the Following
Specify the program file numbers for MCPs A-P and the order in which the
MCPs should be run. This configuration is read before the MCP is executed; if
you make a change to the configuration screen regarding an MCP, that change
takes effect on the next execution of the MCP. You can change the MCP
information on the Controller Configuration screen or through ladder logic.
If you specify an MCP file that does not exist or is not a ladder-logic program,
structured-text program, or SFC file, a major fault is logged in the status file. A
minor fault is also logged if all MCP program files are set to zero.
You can have the same program file number specified more than once as an
MCP. For example, you may want a program to execute frequently and have a
higher priority over other programs.
If you do not want to use multiple main programs, program an SFC (program
file 1), ladder-logic program (program file 2), or structured-text program
(program file 2) and the controller will execute your main program. You do not
need to make any entries on the Controllerr Configuration screen (the
controller automatically enters the first configured program file number in the
first MCP entry).
By setting or resetting the bit in these fields, you tell the controller to skip over
the MCP until the bit is reset. If an MCP program file is inhibited, the controller
skips the file and goes to the next program file.
ATTENTION: If you disable an MCP, outputs remain in the state that they
were in during the last scan (i.e., all actions remain active). Make sure that
you consider any outputs that might be controlled within that MCP before
disabling it. Otherwise, injury to personnel or damage to equipment may result.
Disable an MCP if you temporarily want to hold a machine state, regardless of
transitions (for example, in machine fault conditions). Disabling an MCP also
can help improve scan time; if you know you don't need to run one of your
MCPs every scan, you can disable it until you need it.
To set and reset the bits for Main Control Programs A-P, cursor to the
appropriate field and type 1 to disable (skip) this MCP or 0 to enable (scan) this
MCP.
If the disable bit is set for all the MCP program files (which indicates that all
control programs are to be skipped), a minor fault is logged in the controller
status file.
A 1 in this field tells the controller to skip the I/O scan after this MCP. The
default 0 tells the controller to perform the I/O scan after the corresponding
MCP.
To specify the I/O bit, cursor to the appropriate field and enter 0 or 1.
Status File
S:80-S:127
S:79
S:78