Chapter 9. Diagnostics
446 PACSystems* RX7i, RX3i and RSTi-EP CPU Programmer's Reference Manual GFK-2950C
9.6.2 Executing DLBs
DLB Properties
The properties for an active DLB include Execution Mode, which has the following possible values:
â–ª Sweep (Default) - The DLB executes at a fixed point in the normal Controller sweep, until
explicitly stopped.
▪ Update Rate – Uses the Update Rate defined for the Target. The actual rate varies from a
minimum value equal to the Update Rate to a maximum value of Update Rate + 1 sweep. If the
sweep takes more time than the update rate, the DLB is executed as soon as the user logic
program execution completes in the current sweep.
â–ª Scan Once - The DLB executes exactly one time when the user requests for DLB execution to
start. It then stops executing until it is manually instructed to run again.
Figure 23: Properties of Diagnostic Logic Block (DLB)
Target Properties
The Target properties include DLB Heartbeat, which specifies, in milliseconds, the maximum time the
controller waits for a heartbeat signal from the programmer. If a heartbeat timeout occurs, the DLB
will be stopped and removed from the controller. This insures that DLB execution is stopped in the
event of a communications failure between the programmer and the controller.
With larger applications or a slower PC, some operations such as opening the Controller File Explorer
may cause the DLB Heartbeat to time out. If this happens, you may need to increase the DLB
Heartbeat interval.
The DLB Heartbeat must always be greater than the Update Rate setting for the Target.
Figure 24: DLB Heartbeat Setting
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