Debug files can be the most powerful tools in RSLogix Emulate. This section
provides some strategies for using and manipulating debug files.
When to use debug files
Debug files are ladder logic. Your program uses ladder logic
to control a process; a debug file uses ladder logic to simulate the
process.
Anytime your program acts on a specific sequence of events
(e.g., parts coming down an assembly line), you can simulate the process by
programming ladder logic in a debug file. The following is an example.
Let's suppose you have a process that monitors a part's
progress down an assembly line. There is a bit in your process that controls the
conveyor motor. You have proximity switches that trigger operations when a part
reaches specific areas of the assembly line. A debug file can easily simulate
the part moving down the assembly line.
The first rung is conditioned on the start button for the
process. The process starts, and TR1 starts timing. The preset should be
approximately the time to get a part to the first station.
When TR1 is done timing, the PROX_1 proximity switch turns on.
Since the proximity switch is on, the process at station 1 should activate.
By expanding on this concept, you could emulate the movement
of a part down the entire assembly line.
Emulating block transfer reads
By using debug files, you can emulate the activity of Block
Transfer Read (BTR) instructions.
BTR instructions take a specific number of words from an I/O
module, and place those words in an area of the processor's data table. Since
there is no real I/O while emulating a process, BTR instructions have no data to
read.
To emulate a BTR, place a Sequencer Output (SQO) instruction
in a debug file. Program the SQO so that the destination address of the SQO is
the same as the BTR's Data File address. Enter the test data into the source
words of the SQO. (You might want to enter a few values that are out of range
for your process to test how the ladder logic program handles the erroneous
data.)
When the SQO is executed by the emulator, it passes the data
to the BTR's Data File. Your process can then use the data. You can execute the
SQO automatically by triggering it off the done bit (.DN) of a free running
timer in the same debug file.
Emulating many inputs
You can use the SQO instruction to emulate inputs. Program an
SQO with a destination address in the input data table file. This way, you can
send entire bit patterns to the input words instead of changing the individual
bits.
Note Remember that the
inputs will remain in their last states while emulating. If you want to reset
your inputs, you will need to reset them manually. You could use an FFL
instruction for this purpose.
Emulating fault routines
The status and fault bits in the processor are used by RSLogix
Emulate. If you have a fault routine or shutdown sequence in your ladder
program, you can test it by generating a fault or shutdown signal in a debug
file.
Limit your debug files
If you try to program a single debug file to simulate the
inputs for your entire process, you could end up with a debug file that is
larger than your entire ladder logic program! Try to break down your process
into pieces and create debug files to handle each piece. As you debug the pieces
of your ladder program, you can combine your debug files to test a larger
portion of your ladder program.
