AutomationDirect DL205 User Manual

DL205 User Manual, 4th Edition, Rev. D
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Chapter 3: CPU Specifications and Operations
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Write Outputs to Specialty and Remote I/O
After the CPU updates the outputs in the local and expansion bases, it sends the output point
information that is required by any Specialty modules that are installed. For example, this is
the portion of the scan that writes the output status from the image register to the Remote I/O
racks.
NOTE: It may appear the Remote I/O point status is updated every scan. This is not quite true. The
CPU will send the information to the Remote I/O Master module every scan, but the Remote Master will
update the actual remote modules during the next communication sequence between the master and slave
modules. Remember, the Remote I/O link communication is managed by the Remote Master, not the CPU.
Diagnostics
During this part of the scan, the CPU performs all
system diagnostics and other tasks, such as:
• calculating the scan time
• updating special relays
• resetting the watchdog timer
DL205 CPUs automatically detect and report
many different error conditions. Appendix
B contains a listing of the various error codes
available with the DL205 system.
One of the more important diagnostic tasks is
the scan time calculation and watchdog timer
control. DL205 CPUs have a “watchdog” timer
that stores the maximum time allowed for the
CPU to complete the solve application segment
of the scan cycle. The default value set from the
factory is 200ms. If this time is exceeded the CPU
will enter the Program Mode, turn off all outputs,
and report the error. For example, the Handheld
Programmer displays “E003 S/W TIMEOUT”
when the scan overrun occurs.
You can use AUX 53 to view the minimum, maximum, and current scan time. Use AUX 55
to increase or decrease the watchdog timer value. There is also an RSTWT instruction that can
be used in the application program to reset the watch dog timer during the CPU scan.
Read Inputs
Read Inputs from Specialty I/O
Solve the Application Program
Write Outputs
Diagnostics
Service Peripherals, Force I/O
Write Outputs to Specialty I/O
CPU Bus Communication
Update Clock, Special Relays
Solve PID Loop Equations

AutomationDirect DL205 Specifications

General

Brand	AutomationDirect
Model	DL205
Category	Controller
Language	English