Automationdirect.com DirectLOGIC DL205 Series User Manual page 113

Chapter 3: CPU Specifications and Operations
Program Mode Operation
1
In Program Mode the CPU does not execute
the application program or update the output
modules. The primary use for Program Mode is
2
to enter or change an application program.
You also use the program mode to set up CPU
3
parameters, such as the network address,
retentive memory areas, etc.
4
You can use the mode switch on the DL250–1 and DL260 CPUs to select Program Mode
operation. Or, with the switch in TERM position, you can use a programming device such as
the Handheld Programmer to place the CPU in Program Mode.
5
Run Mode Operation
In Run Mode, the CPU executes the
6
application program, does PID calculations for
configured PID loops (DL250-1/DL260), and
7
updates the I/O system. You can perform many
operations during Run Mode. Some of these
8
include:
Monitor and change I/O point status
9
Update timer/counter preset values
Update Variable memory locations
10
Run Mode operation can be divided into several
key areas. It is very important you understand
how each of these areas of execution can affect
11
the results of your application program
solutions.
12
You can use the mode switch to select Run
Mode operation (DL240, DL250–1 and
13
DL260). Or, with the mode switch in TERM
position, you can use a programming device,
such as the Handheld Programmer to place the
14
CPU in Run Mode.
You can also edit the program during Run
A
Mode. The Run Mode Edits are not "bumpless." Instead, the CPU maintains the outputs in
their last state while it accepts the new program information. If an error is found in the new
B
program, then the CPU will turn all the outputs off and enter the Program Mode.
WARNING: Only authorized personnel fully familiar with all aspects of the application should make
C changes to the program. Changes during Run Mode become effective immediately. Make sure you
thoroughly consider the impact of any changes to minimize the risk of personal injury or damage to
equipment.
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DL205 User Manual, 4th Edition, Rev. B
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Download Program
Read Inputs
Read Inputs from Specialty I/O
Service Peripherals, Force I/O
CPU Bus Communication
Update Clock, Special Relays
Solve the Application Program
Solve PID Equations (DL250-1/DL260)
Write Outputs
Write Outputs to Specialty I/O
Diagnostics