Table of Contents
Advertisement
CPU Operation
Achieving the proper control for your equipment or process requires a good understanding
of how DL05 CPUs control all aspects of system operation. There are four main areas to
understand before you create your application program:
• CPU Operating System — the CPU manages all aspects of system control. A quick overview of all
the steps is provided in the next section.
• CPU Operating Modes — The two primary modes of operation are Program Mode and Run
Mode.
• CPU Timing — The two important areas we discuss are the I/O response time and the CPU scan
time.
• CPU Memory Map — DL05 CPUs offer a wide variety of resources, such as timers, counters,
inputs, etc. The memory map section shows the organization and availability of these data types.
CPU Operating System
At powerup, the CPU initializes the internal electronic
hardware. Memory initialization starts with examining
the retentive memory settings. In general, the content of
retentive memory is preserved, and non-retentive memory
is initialized to zero (unless otherwise specified).
After the one-time powerup tasks, the CPU begins the
cyclical scan activity. The flowchart to the right shows how
the tasks differ, based on the CPU mode and the existence
of any errors. The "scan time" is defined as the average
time around the task loop. Note that the CPU is always
reading the inputs, even during program mode. This allows
programming tools to monitor input status at any time.
The outputs are only updated in Run mode. In program
mode, they are in the off state.
Error detection has two levels. Non-fatal errors are
reported, but the CPU remains in its current mode. If a
fatal error occurs, the CPU is forced into program mode
and the outputs go off.
Chapter 3: CPU Specifications and Operation
DL05 Micro PLC User Manual, 6th Edition, Rev. D
Power up
Initialize hardware
Initialize various memory
based on retentive
configuration
Update input
Service peripheral
Update Special Relays
PGM
Mode?
RUN
Execute program
Update output
Do diagnostics
YES
OK?
NO
Report error, set flag
register, turn on LED
NO
Fatal error
YES
Force CPU into
PGM mode
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
9
9
10
10
11
11
12
12
13
13
14
14
A
a
b
B
c
C
D
D
3-11
Advertisement
Table of Contents
Need help?
Do you have a question about the DL05 and is the answer not in the manual?