Automationdirect.com DirectLOGIC DL205 Series User Manual

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 which 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 200 mS. 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.
DL205 User Manual, 4th Edition, Rev. B
3–26
Chapter 3: CPU Specifications and Operations
1
2
3
4
5
6
7
8
9
10
11
12
13
14
A
B
C
D
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.com DirectLOGIC DL205 Series Specifications

General

Brand	Automationdirect.com
Model	DirectLOGIC DL205 Series
Category	Controller
Language	English