Technical data

Status variables Using the "status variables" function, you can display the current
signal states of certain operands (process variables).
The function activates system checkpoints in the CYCLE, in the
STOP MODE and in the WAIT STATE.
When a checkpoint is reached, the PG displays the present signal
status of the desired process variable. You can specify all process
variables (inputs, outputs, flags, timers, counters and data words). No
addressing error (ADF) is triggered in the process image area when
accessing an address for which there is no I/O available.
The function during program
execution
If the function is activated in the RESTART or RUN modes, program
execution is continued until the system checkpoint "cycle" is reached.
The signal states of the operands are then scanned and output at the
end of the cycle. Inputs are read from the
process image. Providing
the function is not aborted, the signal states are updated during
program execution. In this case the signal states are not scanned at
every system checkpoint.
If the system checkpoint "cycle" is not reached, the signal states are
not output (e.g. in a continuous loop in the user program).
The function in the STOP
mode
If the STATUS VARIABLES function is active in the STOP mode,
the signal states of the operands are output as they stand at the system
checkpoint "stop". The important point to note here is that the
inputs
are scanned directly (not from the process image) and output. This
feature, for example, allows you to check whether an input signal
actually reaches the CPU. Even in multiprocessor operation, you can
specify all inputs regardless of the assignment in DB 1. The outputs
are read from the process image.
The function in the WAIT
STATE
You can also call the STATUS VARIABLES function when the CPU
is in the WAIT STATE caused by the PROGRAM TEST function.
The signal states of the operands are scanned at the system checkpoint
"wait state" and output. As in the stop mode, the inputs are scanned
directly and the outputs are read from the
process image.
Changing the operating
state/terminating the function
When the CPU changes from one mode to another (e.g. RUN →
STOP → MANUAL WARM RESTART), the function remains
activated. STATUS VARIABLES is terminated by pressing the break
key on the programmer.
Note
The variables are not output in every program cycle.
PG Functions
CPU 928B Programming Guide
11 - 16 C79000-B8576-C898-01